SVXLINK.CONF(5)

NAME
svxlink.conf - Configuration file for the SvxLink server

DESCRIPTION
svxlink is a general purpose voice service system for ham radio use. This man-page describe the SvxLink server configuration file format.

SvxLink look for configuration files in a number of places. First it try to find a user specific configuration file. SvxLink will look for a user specific configuration file in: $HOME/.svxlink/svxlink.conf. If no user specific configuration file can be found, SvxLink will look for the system wide configuration file /etc/svxlink/svxlink.conf. The --config command line option may also be used to specify an arbitrary configuration file.

FILE FORMAT
The configuration file is in the famous INI-file format. A generic example of how such a file might look like is shown below.
  [SECTION1]
  VALUE1=1
  VALUE2="TWO "
  VAULE3="Multi "
         "line"

  [SECTION2]
  VALUE1=2 This is a simple format that contain name=value pairs that belong to a section. In written text, a specific configuration variable can be referred to as SECTION1/VALUE2 meaning "configuration variable VALUE2 in section SECTION1".

The same variable name can exist in two different sections. For example VALUE1 in section SECTION1 have the value 1 and VALUE1 in section SECTION2 have the value 2. Values containing spaces at the beginning or end of the line must be surrounded by citation characters (see SECTION1/VALUE2). Likewise with a multi line value (see SECTION1/VALUE3).

CONFIGURATION VARIABLES
Here is the description of all configuration variables that SvxLink understands. The configuration variables are described section for section.

  GLOBAL
The GLOBAL section contains application global configuration data.

MODULE_PATH
    Specify where the SvxLink modules can be found. If MODULE_PATH is not specified, the standard search paths for library files will be used. If that also fails a hard-coded default will be used. What that default is depend on the architecture but typically on a x86_64 system it is /usr/lib64/svxlink. Leaving this variable unset should work in most cases.

LOGIC_CORE_PATH
    Specify where the SvxLink logic core plugins can be found. If not set, a hard-coded default will be used. What that default is depend on the architecture but typically on an x86_64 system it is /usr/lib64/svxlink. Leaving this variable unset should work in most cases. If this variable is set to empty, the standard search paths for library files will be used (see man 3 dlopen).

LOGICS
    Specify a comma separated list of logic cores that should be created. The logic core is the thing that ties the transceiver and the voice services (modules) together. It contains the rules for how the radio interface should be handled. The specified name of a logic core must have a corresponding section specified in the config file. This is where the behavior of the logic core is specified.

CFG_DIR
    Specify the path to a directory that contain additional configuration files. If a relative path is specified, the path will be relative to the directory where the main configuration file is at. All files in the specified directory will be read as additional configuration. Filenames starting with a dot (hidden files) or not ending in .conf are ignored.

TIMESTAMP_FORMAT
    This variable specifies the format of the time-stamp that is written in front of each row in the log file. The format string is in the same format as specified in the strftime(3) manual page. The default is "%c" which is described as: "the preferred date and time representation for the current locale". The environment variables LC_TIME, LC_ALL and LANG will affect how this time format will look. For example, setting LC_TIME="sv_SE.UTF8" will give you Swedish time-stamp representation. Other examples of format specifiers are:

    •   %d - The day of the month as a decimal number (range 01 to 31)

    •   %b - The abbreviated month name according to the current locale

    •   %Y - The year as a decimal number including the century

    •   %H - The hour as a decimal number using a 24-hour clock (range 00 to 23)

    •   %M - The minute as a decimal number (range 00 to 59)

    •   %S - The second as a decimal number (range 00 to 60)

    •   %f - Fractional seconds in millisecond resolution (000-999)

    The last one (%f) is a SvxLink specific formatting specifier. Example: TIMESTAMP_FORMAT="%d %b %Y %H:%M:%S.%f" would give a time-stamp looking something like: "29 Nov 2005 22:31:59.875".

CARD_SAMPLE_RATE
    This configuration variable determines the sampling rate used for audio input/output. SvxLink always work with a sampling rate of 16kHz internally but there still are some benefits from using a higher sampling rate. On some sound cards the filters look pretty bad at 16kHz and the amplitude response will not be uniform which among other things can cause problems for the software DTMF decoder. Some sound cards also sound very bad at 16kHz due to insufficient anti-alias filtering or resampling effects. These, often cheaper, sound cards sound OK at 48kHz. The downside of choosing a higher sampling rate is that it puts a little bit more load on the CPU so if you have a very slow machine (<300MHz), it might not have the computational power to handle it. Supported sampling rates are: 16000 and 48000.

CARD_CHANNELS
    Use this configuration variable to specify how many channels to use when opening a sound card. For normal sound cards the only practical values to use are 1 for mono and 2 for stereo. The latter is the default. When using the sound card in stereo mode it is possible to use the left and right channels independently to drive two transceivers. When using the sound card in mono mode, both left and right channels transmit/receive the same audio.

LOCATION_INFO
    Enter the section name that contains information required for transferring positioning data to location servers. Setting this item makes the system visible on the EchoLink link status page and the APRS network.

LINKS
    Enter here a comma separated list of section names that contains the configuration information for linking logics together (see Logic Linking).

  Common Logic configuration variables
A logic core is what define how SvxLink should behave on the RF channel. The SvxLink server can handle more than one logic core and so can be connected to more than one transceiver. When configured, a logic core is loaded at runtime as a plugin. See the LOGIC_CORE_PATH configuration variable for more information on how SvxLink find the logic core plugins.

The configuration variables below are common to all logic types. Configuration variables that are specific to a certain logic core type are described below in a section of its own.

TYPE
    The type of logic core this is. The documentation for the specific logic core type you want to use describe what to write here.

RX  Specify the configuration section name of the receiver to use. All configuration for the receiver is done in the specified configuration section.

TX  Specify the configuration section name of the transmitter to use. All configuration for the transmitter is done in the specified configuration section.

MODULES
    Specify a comma separated list of configuration sections for the modules to load. This tells SvxLink which modules to actually load on startup.

CALLSIGN
    Specify the callsign that should be announced on the radio interface.

SHORT_VOICE_ID_ENABLE
    A basic toggle to enable the voice ID announcement during the short ID announcements. Set value to "1" to enable the voice option, and "0" to disable.

SHORT_CW_ID_ENABLE
    A basic toggle to enable the CW ID announcement during the short ID announcements. Set value to "1" to enable the CW option, and "0" to disable.

SHORT_ANNOUNCE_ENABLE
    A basic toggle to enable the custom announcement during the short ID announcements. Set value to "1" to enable the announcement option, and "0" to disable.

SHORT_ANNOUNCE_FILE
    The full path to a file to use for custom announcements broadcasted during a routine short ID.

LONG_VOICE_ID_ENABLE
    A basic toggle to enable the voice ID announcement during the long ID announcements. Set value to "1" to enable the voice option, and "0" to disable.

LONG_CW_ID_ENABLE
    A basic toggle to enable the CW ID announcement during the long ID announcements. Set value to "1" to enable the CW option, and "0" to disable.

LONG_ANNOUNCE_ENABLE
    A basic toggle to enable the custom announcement during the long ID announcements. Set value to "1" to enable the announcement option, and "0" to disable.

LONG_ANNOUNCE_FILE
    The full path to a file to use for custom announcements broadcasted during a routine short ID.

CW_AMP
    Specify the amplitude of the CW that should be used during any cw traffic, typically announcements. The amplitude is specified in dB. Default: -6.

CW_PITCH
    Specify the pitch (frequency in Hz) of the CW that should be used during any CW traffic, typically announcements. Default: 800.

CW_CPM
    Specify the Characters Per Minute of the CW that should be used during any CW traffic, typically announcements. If both CW_WPM and CW_CPM is set, CW_CPM will be used. Default: 100.

CW_WPM
    Specify the Words Per Minute of the CW that should be used during any CW traffic, typically announcements. If both CW_WPM and CW_CPM is set, CW_CPM will be used. Default: 20.

PHONETIC_SPELLING
    Specify if the spelling of callsign and other words should be announced on the radio interface using phonetic or non-phonetic spelling. "1" to use phonetic sounds (legacy default), or "0" to use non-phonetic sounds. Note that this option may not be available for all language packs.

TIME_FORMAT
    Specify what format the time should be announced as, valid options are "12"/"24". NOTE: may not work for all language packs

SHORT_IDENT_INTERVAL
    The number of minutes between short identifications. The purpose of the short identification is to just announce that the station is on the air. Typically just the callsign is transmitted. For a repeater a good value is ten minutes and for a simplex node one time every 60 minutes is probably enough. The LONG_IDENT_INTERVAL must be an even multiple of the SHORT_IDENT_INTERVAL so if LONG_IDENT_INTERVAL is 60 then the legal values for SHORT_IDENT_INTERVAL are: 1, 2, 3, 4, 5, 6, 10, 12, 15, 20, 30, 60. If unset or set to 0, disable short identifications.

LONG_IDENT_INTERVAL
    The number of minutes between long identifications. The purpose of the long identification is to transmit some more information about the station status (new voice mails etc). The time of day is also transmitted. A good value here is 60 minutes. If unset or set to 0, disable long identifications.

IDENT_ONLY_AFTER_TX
    This feature controls when identification is done. By default, identification is done every time the SHORT_IDENT_INTERVAL expires. If this feature is enabled, identification will be done only if there has been a recent transmission. This feature is good for nodes using an RF link to provide echolink to a repeater. Often, in this situation, it is not desirable for the link to identify unless legally necessary. Note that SHORT_IDENT_INTERVAL still have to be set for this feature to work. That config variable will then be interpreted as the minimum number of seconds between identifications. The LONG_IDENT_INTERVAL will not be affected by this parameter.

EXEC_CMD_ON_SQL_CLOSE
    Specify a time, in milliseconds, after squelch close after which entered DTMF digits will be executed as a command without the need to send the # character. To disable this feature, either comment out the configuration row or set it to a value less or equal to zero.

EVENT_HANDLER
    Point out the TCL event handler script to use. The TCL event handler script is responsible for playing the correct audio clips when an event occur. The default location is /usr/share/svxlink/events.tcl.

DEFAULT_LANG
    Set the default language to use for announcements. It should be set to an ISO code (e.g. sv_SE for Swedish). If not set, it defaults to en_US which is US English.

RGR_SOUND_DELAY
    The number of milliseconds to wait after the squelch has been closed before a roger beep is played. The beep can be disabled by specifying a value of -1 or commenting out this line. Often it is best to use the SQL_HANGTIME receiver configuration variable to specify a delay instead of specifying a delay here. This configuration variable should then be set to 0.

REPORT_CTCSS
    If set, will report the specified CTCSS frequency upon manual identification (* pressed). It is possible to specify fractions using "." as decimal comma. Disable this feature by commenting out (#) this configuration variable.

TX_CTCSS
    This configuration variable controls if a CTCSS tone should be transmitted. Use a comma separated list (no spaces!) to specify when to transmit a CTCSS tone. These are the possible values: SQL_OPEN, LOGIC, MODULE, ANNOUNCEMENT or ALWAYS. Commenting out this configuration variable will disable CTCSS transmit. The tone frequency and level is configured in the transmitter configuration section.

    •   SQL_OPEN will transmit CTCSS tone when the squelch is open. This is only useful on a repeater. On a simplex node it doesn't make much sense.

    •   LOGIC will transmit CTCSS tone when there is incoming traffic from another logic core.

    •   MODULE will transmit CTCSS tone when there is incoming traffic from a module.

    •   ANNOUNCEMENT will transmit CTCSS tone when an announcement is being played. Repeater idle sounds and roger beeps will not have tone sent with them though.

    •   ALWAYS will always transmit a CTCSS tone as soon as the transmitter is turned on.

MACROS
    Point out a section that contains the macros that should be used by this logic core. See the section description for macros below for more information.

FX_GAIN_NORMAL
    The gain (dB) to use for audio effects and announcements when there is no other traffic. This gain is normally set to 0dB which means no gain or attenuation.

FX_GAIN_LOW
    The gain (dB) to use for audio effects and announcements when there is other traffic. This gain is normally set to something like -12dB so that announcements and audio effects are attenuated when there is other traffic present.

QSO_RECORDER
    The QSO recorder is used to write all received audio to files on disk. The format for this configuration variable is <command>:<config section>. The specified command is used to activate or deactivate the QSO recorder. If the command for example is set to 8, 81 will activate the recorder and 80 will deactivate it. The command may also be left out. It will then not be possible to control the QSO recorder using DTMF commands. Even if the command is left out the colon must always be specified. The config section point out a section in the configuration file that holds configuration for the QSO recorder. Have a look at the QSO Recorder Section documentation for more information. Example: QSO_RECORDER=8:QsoRecorder

SEL5_MACRO_RANGE
    Define two comma separated values here to map the Sel5 tone call to your macro area. E.g. if you have defined: SEL5_MACRO_RANGE=03400,03499 then all incoming Sel5 tone sequences from 03400 to 03499 are mapped to the macros section (refer to Macros Section, next chapter). Other sequences but the one defined under OPEN_ON_SEL5 are ignored so it can be used to call other stations via the repeater without a repeater reaction.

ONLINE_CMD
    Define a DTMF command that is used to switch the node between online and offline mode. When in the off-state, the transmitter will not be turned on by any event. If a module is active when the node is brought offline, it will be deactivated and no module activation will be allowed in offline mode. No other commands than the online command will be accepted in the offline state. If the command for example is set to 998877 then 9988771 will set the node online and 9988770 will set it offline. If a module is active or if the ACTIVATE_MODULE_ON_LONG_CMD is used, the command must be prefixed with a star to work as expected. The star means "force core command".

ONLINE
    Set to 0 to make SvxLink start offline. Settable at runtime. Default is 1 (online).

STATE_PTY
    Using this configuration variable it is possible to specify a path to a UNIX 98 PTY that SvxLink state events is published to. The published events is in a simple text format using a space separated list of values. SvxLink will create a softlink to the actual slave PTY. For that reason, SvxLink must have write permissions in the directory where the softlink should be created. Monitoring the PTY output is as simple as doing a cat /path/to/pty after starting SvxLink. See STATE PTY FORMAT for more information on the format of the state messages. Example: STATE_PTY=/tmp/state_pty

DTMF_CTRL_PTY
    Using this configuration variable it is possible to specify a path to a UNIX 98 PTY that allows a dtmf control of each single SvxLink logic. SvxLink will create a softlink to the actual slave PTY. For that reason, SvxLink must have write permissions in the directory where the softlink should be created. Sending commands to the PTY is as simple as doing a echo '*1#' > /path/to/pty after starting SvxLink. The device works bidirectional, received dtmf characters (from Rf) are output via this interface. Example: DTMF_CTRL_PTY=/dev/shm/dtmf_ctrl

CTCSS_TO_TG
    Use this configuration variable to specify a comma separated list of pairs of tone frequencies and talk groups. When one of the tone frequencies is detected, the corresponding talk group will be associated with the received audio. This can be used for example by ReflectorLogic to automatically switch to a talk group when one of the specified tone frequencies is received. You also must configure CTCSS_FQ for all receivers to open the squelch on the same tone frequencies. Otherwise it will not work. Also, the CTCSS squelch detector must actually be used in the receiver. It's not enough to just set CTCSS_FQ. Example: CTCSS_TO_TG=127.3:9993,136.5:9995

CTCSS_TO_TG_DELAY
    The delay for reporting detected talkgroup from when a CTCSS tone is detected. If the squelch close before the delay time has expired, no talkgroup will be reported. Default: 1000. Example: CTCSS_TO_TG_DELAY=0

  Simplex Logic Section
The Simplex Logic section contains configuration data for a simplex logic core. The name of the section, which in the example configuration file is SimplexLogic, must have a corresponding list item in the GLOBAL/LOGICS config variable for this logic core to be activated. The name "SimplexLogic" is not magic. It could be called what ever you like but it must match the namespace name in the SimplexLogic.tcl script. The configuration variables below are those that are specific for a simplex logic core.

TYPE
    The type for a simplex logic core is always Simplex.

MUTE_RX_ON_TX
    Set to 1 to mute the receiver when the transmitter is transmitting (default) or set it to 0 to make the RX active during transmissions. One might want to set this to 0 if the link is operating on a split frequency. Then the link can accept commands even when it's transmitting. The normal setting is 1, to mute the RX when transmitting.

MUTE_TX_ON_RX
    Set to 1 to mute the transmitter when the squelch is open (default) or set it to 0 to make the TX active during squelch open. One might want to set this to 0 if the link is operating on a split frequency or if it's connected to some full duplex device. The normal setting is 1, to mute the TX when the squelch is open.

RGR_SOUND_ALWAYS
    Set to 1 to always send roger sound after squelch close, even when no module is active.

COMMAND_PTY
    Using this configuration variable it is possible to specify a path to a UNIX 98 PTY that can be used to send commands to a SvxLink logic core. SvxLink will create a softlink to the actual slave PTY. For that reason, SvxLink must have write permissions in the directory where the softlink should be created. Sending commands to the PTY is as simple as doing a echo 'THE COMMAND TO EXECUTE' > /path/to/pty after starting SvxLink. Valid commands:

    •   CFG <section> <tag> <value> -- Set a configuration variable. Only a few configuration variables support being set at runtime. Example: CFG RepeaterLogic ONLINE 0.

    •   EVENT <event name> [<arg> ...] -- Call an event handler (TCL function). It is important to specify the correct TCL namespace for the function to be found. If no namespace is given, the namespace of the current logic core will be added, e.g. "manual_identification" is the same as "RepeaterLogic::manual_identification" if the logic core namnespace is "RepeaterLogic". To call a function in the root namespace, the function name must be prepended with "::". Example: EVENT ::playNumber -42.5.
Example: COMMAND_PTY=/dev/shm/repeater_logic_ctrl

  Repeater Logic Section
A Repeater Logic section contains configuration data for a repeater logic core. The name of the section, which in the example configuration file is RepeaterLogic, must have a corresponding list item in the GLOBAL/LOGICS config variable for this logic core to be activated. The name "RepeaterLogic" is not magic. It could be called what ever you like but it must match the namespace name in the RepeaterLogic.tcl script. The configuration variables below are those that are specific for a repeater logic core.

TYPE
    The type for a repeater logic core is always Repeater.

NO_REPEAT
    Set this to 1 if you do NOT want SvxLink to play back the incoming audio. This can be used when the received audio is directly coupled by hardware wiring to the transmitter. What you win by doing this is that there is zero delay on the repeated audio. When the audio is routed through SvxLink there is always an amount of delay. What you loose by doing this is the audio processing done by SvxLink (e.g. filtering, DTMF muting, squelch tail elimination) and the ability to use remote receivers.

IDLE_TIMEOUT
    The number of seconds the repeater should have been idle before turning the transmitter off.

OPEN_ON_1750
    Use this configuration variable if it should be possible to open the repeater with a 1750Hz tone burst. Specify the number of milliseconds the tone must be asserted before the repeater is opened. Make sure that the time specified is long enough for the squelch to have time to open. Otherwise the repeater will open "too soon" and you will hear an ugly 1750Hz beep as the first thing. A value of 0 will disable 1750 Hz repeater opening.

OPEN_ON_CTCSS
    Use this configuration variable if it should be possible to open the repeater using a CTCSS tone (PL). The repeater will activate after the specified number of milliseconds on detection of any of the CTCSS frequencies specified in the receiver configuration. Note that the CTCSS squelch must actually be used as a squelch detector in the receiver. It's not enough to just set CTCSS_FQ.

OPEN_ON_DTMF
    Use this configuration variable if it should be possible to open the repeater with a DTMF digit. Only one digit can be specified. DTMF digits pressed when the repeater is down will be ignored.

OPEN_ON_SEL5
    Use this configuration variable if you want to open your repeater by using a selective tone call that is often used in commercial radio networks. Example: OPEN_ON_SEL5=03345 opens your repeater only if that sequence has been received. You can use sequence lengths from 4 to 25.

CLOSE_ON_SEL5
    Use this configuration variable if you want to close your repeater by using a selective tone call that is often used in commercial radio networks. Example: CLOSE_ON_SEL5=03345 closes your repeater if that sequence has been received. You can use sequence lengths from 4 to 25.

OPEN_ON_SQL
    Use this configuration variable if it should be possible to open the repeater just by keeping the squelch open for a while. The value to set is the minimum number of milliseconds the squelch must be open for the repeater to open.

OPEN_ON_SQL_AFTER_RPT_CLOSE
    Activate the repeater on just a squelch opening if there have been no more than the specified number of seconds since the repeater closed.

OPEN_SQL_FLANK
    Determines if OPEN_ON_SQL and OPEN_ON_CTCSS should activate the repeater when the squelch open or close. If set to OPEN, the repeater will activate and start retransmitting audio immediately. No identification will be sent. If set to CLOSE, the repeater will not activate until the squelch close. An identification will be sent in this case.

IDLE_SOUND_INTERVAL
    When the repeater is idle, a sound is played. Specify the interval in milliseconds between playing the idle sound. An interval of 0 disables the idle sound.

SQL_FLAP_SUP_MIN_TIME
    Flapping squelch suppression is used to close the repeater down if there is interference on the frequency that open the squelch by short bursts. This configuration variable is used to specify the minimum time, in milliseconds, that a transmission must last to be classified as a real transmission. A good value is in between 500-2000ms.

SQL_FLAP_SUP_MAX_COUNT
    Flapping squelch suppression is used to close the repeater down if there is interference on the frequency that open the squelch by short bursts. This configuration variable is used to specify the maximum number of consecutive short squelch openings allowed before shutting the repeater down. A good value is in between 5-10.

ACTIVATE_MODULE_ON_LONG_CMD
    This configuration variable activate a feature that might help users not aware of the SvxLink command structure. The idea is to activate the specified module when a long enough command has been received. The typical example is an EchoLink user that is used to just typing in the node ID and then the connection should be established right away. Using this configuration variable, specify a minimum length and a module name. If no module is active and at least the specified number of digits has been entered, the given module is activated and the command is sent to it. To be really useful this feature should be used in cooperation with EXEC_CMD_ON_SQL_CLOSE. For example, if this configuration variable is set to "4:EchoLink" and the user types in 9999, the EchoLink module is first activated and then the command 9999 is sent to it, which will connect to the ECHOTEST server.

IDENT_NAG_TIMEOUT
    Tell repeater users that are not identifying to identify themselves. The number of seconds to wait for an identification, after the repeater has been activated, is set using this configuration variable. A valid identification is considered to be a transmission longer than the time set by the IDENT_NAG_MIN_TIME configuration variable. We don't know if it's really an identification but it's the best we can do. Setting it to 0 or commenting it out disables the feature.

IDENT_NAG_MIN_TIME
    This is the minimum time, in milliseconds, that a transmission must last to be considered as an identification. This is used as described in the IDENT_NAG_TIMEOUT configuration variable.

  ReflectorLogic
The ReflectorLogic is used to connect to an SvxReflector server. The SvxReflector will distribute all audio to all connected nodes. To actually send audio to the reflector from a logic core, set up a link between the two logics using LogicLinking. More than one logic core can be connected.

SvxReflector also offer traffic separation using talk groups so that multiple QSOs can be ongoing through the same reflector server without interfering with each other. The set of talk groups that a node monitors for activity is configurable so that a talk group can be automatically selected when it's active. After a configurable timeout the node will return to monitor all configured talk groups if there is no activity on the currently selected talk group. Which talk group to select for outgoing traffic for a node can be set to a default, selected by the CTCSS tone used and/or selected using DTMF commands. The DTMF commands are entered through the logic linking definition associated with the reflector. So if a command prefix of 9 have been specified for a link, selecting talk group 888 will be achieved by entering the command 91888#.

The reflector connection will be authenticated using X.509 certificates. Both the server and the client require authentication. The AUTH_KEY authentication method that was previously used is deprecated. The certificate generation process is mostly automated. The contents of the certificate can be customized using the configuration variables with the name prefix CERT_. Default values are good in most cases. CERT_EMAIL may be good to specify so that the SvxLink node owner can be contacted. Ask the reflector sysop what the convention is.

TYPE
    The type for a reflector logic core is always Reflector.

DNS_DOMAIN
    The domain of the SvxReflector server to connect to. To make this work, the DNS domain have to be configured with SRV records for all reflector servers serving that domain. For example, if the domain is example.org, there must be one or more SRV entries in the DNS with the name _svxreflector._tcp.example.org. Each SRV record contain information about hostname, port, priority and weight. The priority determine in which order SvxLink will try to connect to the servers. The weight is used to give different servers with the same priority a probability for how often it will be selected.

HOSTS
    A comma separated list of hostname:port pairs of the reflector servers. IP address also work. If port is not specified the value of HOST_PORT will be used as a default. If DNS_DOMAIN is also specified, the values in the HOSTS list will be added to the list looked up in the DNS. The order of the entries depend on HOST_PRIO, HOST_PRIO_INC and HOST_WEIGHT.

HOST_PRIO
    The priority value to use for entries in the HOSTS list. The priority determine in which order SvxLink will try to connect to the specified servers. See also HOST_PRIO_INC. Default: 100.

HOST_PRIO_INC
    The value with which to increase the priority value for each entry in the HOSTS list. The first value will be the one specified by HOST_PRIO. Default: 1.

HOST_WEIGHT
    The weight value will determine how often a server will be selected in comparison to servers with the same priority. This variable is only useful when one want to set the weight in relation to other SRV records looked up in the DNS. The weight values for entries in the HOSTS list will always be the same.

HOST_PORT
    The default TCP/UDP port number used by the reflector server. The client do not need to open any ports in the firewall. Default: 5300.

CALLSIGN
    The callsign of this node. The callsign also serves as the username when authenticating to the SvxReflector server.

AUTH_KEY
    The authentication key, or password, used when authenticating to the SvxReflector server. When connecting to a modern reflector server, certificates are used instead of an AUTH_KEY. Then this configuration variable should be left unset.

JITTER_BUFFER_DELAY
    A jitter buffer is used to prevent gaps in the audio when the network connection do not provide a steady flow of data. Set this configuration variable to the number of milliseconds to buffer before starting to process the audio. Default: 0.

DEFAULT_TG
    The node will select this talk group on local incoming traffic if no other talk group is currently selected. Default: 0 (no talk group).

MONITOR_TGS
    A comma separated list of talk groups which the node will monitor for activity when no other talk group is selected. It is also possible to mark talk groups as more prioritized than others by adding one or more plus signs after the talk group number. More plus signs mean higher priority. While a talk group is selected, and there are activity on a talk group with higher priority, the higher prio talk group will be selected unless there have been local activity on the node. Example:
      MONITOR_TGS=112++,240,2403+,2403123 will monitor the TGs for Sweden, Sweden district 3 and a specific TG #2403123. Traffic on talk group 2403 will be prioritized and 112 will have the highest priority.

TG_SELECT_TIMEOUT
    The number of seconds after which a selected talk group will be unselected. The node will return to talk group 0 (no talk group) and start monitoring the configured talk groups again. The value must be larger than zero. Default: 30 seconds.

TG_SELECT_INHIBIT_TIMEOUT
    Talkgroup selection is inhibited when there is activity on the local frequency that does not activate a talkgroup. Only activation due to remote activity (monitoring) is inhibited. A talkgroup can be activated as usual by using any method for local activation. This feature make it possible to conduct a local QSO without being disturbed by remote reflector traffic. Use this configuration variable to set the number of seconds of inactivity before the node will go back to monitoring remote talkgroup activity. The default value is taken from TG_SELECT_TIMEOUT if this variable is not set. Setting a value of 0 will disable the feature entirely.

ANNOUNCE_REMOTE_MIN_INTERVAL
    The minimum number of seconds between announcements of the same TG for remote TG activations. If the same TG is remotely activated repeatedly it will not be announced until at least the number of seconds specified in this configuration variable have passed.

NODE_INFO_FILE
    The configuration file to use for sending information regarding this client to the reflector server. This is not a required configuration. It is mostly free-form JSON but the general structure should be kept so that SvxLink and the reflector server can fill in dynamic information about the node like signal strengths for receivers. Use the default node_info.json as a template. You can add more information rather freely but don't change the overall structure.

MUTE_FIRST_TX_LOC
    Mute the first transmission after selecting a talk group due to local activity. This feature is good to have enabled for a number of reasons. One reason is to suppress short openings of a talk group when someone just make a single transmission to test the local node. Another reason is for to allow someone to submit DTMF commands to the node without disturbing the reflector network. An example is that someone activates a talk group using CTCSS but then immediately select another talk group using DTMF. In that case no transmission will be made on the first talk group. This feature is enabled by default.

MUTE_FIRST_TX_REM
    Mute the first transmission after selecting a talk group due to remote activity. This feature can be enabled to let local node users enter DTMF commands without disturbing an active talk group. As an example, the local node monitors a talk group that is active. However, no one on the local node participates in the QSO and a local user want to select another talk group. With this feature enabled it is possible to do that without transmitting into the reflector network while entering DTMF commands. This feature is not enabled by default since it is a bit unintuitive. If a local user hear a call and want to answer that call, he must first make a short transmission to "open up" the local node. This is easy to forget.

TMP_MONITOR_TIMEOUT
    This configuration variable determines after how many seconds a manually added temporary talk group monitor will time out. Set to 0 to disable this feature. Default is 3600, one hour.

UDP_HEARTBEAT_INTERVAL
    The number of seconds between UDP heartbeat messages sent to the reflector server. This configuration variable can normally be left at the default value but if you get frequent disconnects due to UDP heartbeat timeout it may help to lower this value. Default: 15

QSY_PENDING_TIMEOUT
    Set to the number of seconds to enable following a QSY request on squelch activity. That is, after a remote QSY request, during the configured number of seconds, it will be possible to follow a QSY request by just pushing the PTT instead of having to use DTMF commands. Note that the timer starts when the QSY request is received so the time it takes to play the QSY announcement is also included in the timeout time. A good value is within 10 to 15 seconds. Default is -1 (disabled).

VERBOSE
    Set to 0 to suppress reflector leave/join printouts.

It is also possible to set audio codec parameters using the same configuration variables as documented for networked receivers and transmitters. For example, to lighten the encoder CPU load for the Opus encoder, set OPUS_ENC_COMPLEXITY to something lower than 9.

CERT_PKI_DIR
    The path to the directory where PKI (Public Key Infrastructure) files will be stored. Example: CERT_PKI_DIR=/var/lib/svxlink/pki

CERT_KEYFILE
    The path to the private key for the X.509 client certificate. This file will be auto generated if it does not exist. It must be kept secure since this is what authenticates your node. It must NOT be sent in the clear over the internet for example. Also, if you loose this file you will have to ask the reflector sysop to issue a new certificate for the new key. Example: CERT_KEYFILE=/var/lib/svxlink/pki/MYCALL.key

CERT_CSRFILE
    The path to the certificate signing request for the X.509 client certificate. This file will be auto generated if it does not exist or if the configuration information has been changed. When a new CSR is generated, the reflector sysop need to sign it before it will become active. Example: CERT_CSRFILE=/var/lib/svxlink/pki/MYCALL.csr

CERT_CRTFILE
    The path to the X.509 client certificate. This file is a public file that is used to identify your node. It is sent to the reflector during the authentication procedure. It will be created after the CSR has been signed by the reflector sysop. The reflector will send this file to the client during the authentication procedure if it's missing on the node or if the certificate has been updated. Example: CERT_CRTFILE=/var/lib/svxlink/pki/MYCALL.crt

CERT_CAFILE
    The path to the X.509 certificate bundle. This file contains one or more certificates that is used to verify the authenticity of the reflector server. Example: CERT_CAFILE=/var/lib/svxlink/pki/ca-bundle.pem

CERT_DOWNLOAD_CA_BUNDLE
    The CA bundle is by default downloaded from the reflector server if it's missing or need to be updated. Set this configuration variable to 0 to disable that behaviour. That should be done if you want to provide your own CA bundle.

CERT_SUBJ_GN, CERT_SUBJ_givenName
    The name of the person, with which s/he is normally called, owning the SvxLink node. Example: CERT_SUBJ_GN=John

CERT_SUBJ_SN, CERT_SUBJ_surname
    The family name of the person owning the SvxLink node. Example: CERT_SUBJ_SN=Doe

CERT_SUBJ_OU, CERT_SUBJ_organizationalUnitName
    The name of the organizational unit to which the SvxLink node belongs. That may be a subdivision of a ham radio organization for example. Example: CERT_SUBJ_OU="VHF/UHF Unit"

CERT_SUBJ_O, CERT_SUBJ_organizationName
    The name of the organization to which the SvxLink node belongs. That may be a ham radio club for example. Example: CERT_SUBJ_O=SSA

CERT_SUBJ_L, CERT_SUBJ_localityName
    The name of the city where the SvxLink node is located. Example: CERT_SUBJ_L=Stockholm

CERT_SUBJ_ST, CERT_SUBJ_stateOrProvinceName
    The name of the state or province where the SvxLink node is located. Example: CERT_SUBJ_ST=Södermanland

CERT_SUBJ_C, CERT_SUBJ_countryName
    The ISO 3166 country code for the country where the SvxLink node is located. Example: CERT_SUBJ_C=SE

CERT_EMAIL
    A comma separated list of email addresses where the SvxLink node owners can be reached. Example: CERT_EMAIL=mycall1@example.com,mycall2@example.com

  QSO Recorder Section
The QSO recorder is used to record all received audio to files on disk. All audio from receivers, modules and logic links are recorded. Announcements are not recorded.

REC_DIR
    Use this configuration variable to specify in which directory to write the audio files. A good place is /var/spool/svxlink/qso_recorder.

MIN_TIME
    If the duration of the recorded content for a file is less then MIN_TIME milliseconds, the file will be deleted when the file is closed. Default: 0 (empty files will be deleted).

MAX_TIME
    Setting this configuration variable will set an upper limit for the file size of a recording. No more than MAX_TIME seconds of content will be recorded to a single file. When the maximum time have been reached, the file is closed and another file is created. Note that it is not the maximum time that the recording has been active that we are setting a limit for but rather how much content that have been recorded to the file. If nothing is recorded, the file can stay open indefinitely. Default: 0 (no limit)

SOFT_TIME
    To not get abrupt breaks in recordings it is possible to set a soft break time. Let's say that MAX_TIME is set to 3600 seconds (one hour). If we set SOFT_TIME to 300 seconds (five minutes) the QSO recorder try to close the file on a squelch close somewhere between 55 and 60 minutes. In this way we may avoid getting transmissions split up between files. Default: 0 (no limit)

MAX_DIRSIZE
    Specify the maximum total size in megabytes of the files in the recording directory. If the limit is exceeded, the oldest files are deleted. The directory size is checked upon file close so the size may grow temporarily past the limit with at most the size of one recorded file. Only files which have a filename starting with "qsorec_" will be considered for deletion. If using an ENCODING_CMD, make sure that the "qsorec_" prefix is not removed from the target filename unless you really want the MAX_DIRSIZE feature to skip them. Default: 0 (no limit)

DEFAULT_ACTIVE
    If this configuration variable is set to 1, the QSO recorder will be activated by default when SvxLink start. Default: 0 (default inactive)

TIMEOUT
    If a timeout is specified, the activation state of the QSO recorder will return to the value specified in the DEFAULT_ACTIVE configuration variable when the node has been idle for the specified number of seconds. When DEFAULT_ACTIVE is unset or 0, if the QSO recorder is manually activated it will be automatically deactivated after the specified amount of time of inactivity. When DEFAULT_ACTIVE is set to 1, if the QSO recorder is manually deactivated it will be automatically activated after the specified amount of time of inactivity. Default: 0 (no timeout)

QSO_TIMEOUT
    Set this configuration variable if you want to close the currently opened file and open a new one after each QSO. The number of seconds the node should be idle before closing the file should be specified. Default: 0 (no QSO timeout)

ENCODER_CMD
    Specify a command to be executed after a new wav file have been written to disk. This makes it possible to use an external encoder utility to encode the wav file to another format. Even though this configuration variable was added to run an external encoder it could do more complicated things with the file if needed. A couple of examples would be to transfer the file to another computer or to send a notification e-mail. If the command line get too complicated it may be a good idea to write a script instead. The encoder command will be run under a shell so normal shell operators like redirects and pipes may be used. The shell specified in the SHELL environment variable will be used and if not set, /bin/sh will be used. The "-c" command line option will be added so the complete command will look something like: $SHELL -c "$ENCODER_CMD". A number of %-codes can be included in the command. They have the following meaning:

    •   %f - The full filename with full path

    •   %d - The directory part (what REC_DIR is set to)

    •   %b - The basename, that is, the filename without path and extension

    •   %n - The filename without path but with extension

    The encoder will be started in the background and it will not be stopped even if SvxLink exits. It will run in the background until it's done. As long as SvxLink is running it is monitoring the encoding processes. If a process run for longer than one hour it will be killed. Note that SvxLink will never remove the original recording so that have to be done in the encoder command. Here are a couple of examples:
     ENCODER_CMD=/usr/bin/oggenc -Q \"%f\" && rm \"%f\"
     ENCODER_CMD=/usr/bin/lame --quiet \"%f\" \"%d/%b.mp3\" && rm \"%f\"
     ENCODER_CMD=/usr/bin/speexenc \"%f\" \"%d/%b.spx\" 2>/dev/null && rm \"%f\"
     ENCODER_CMD=/usr/bin/opusenc \"%f\" \"%d/%b.opus\" 2>/dev/null && rm \"%f\"

  Macros Section
A macros section is used to declare macros that can be used by a logic core. The logic core points out the macros section to use by using the MACROS configuration variable. The name of the MACROS section can be chosen arbitrarily as long as it match the MACROS configuration variable in the logic core configuration section. There could for example exist both a [RepeaterLogicMacros] and a [SimplexLogicMacros] section.

A macro is a kind of shortcut that can be used to decrease the amount of key presses that have to be done to connect to common EchoLink stations for example. On the radio side, macros are activated by pressing "D" "macro number" "#". A macros section can look something like the example below. Note that the module name is case sensitive.
  [Macros]
  1=EchoLink:9999#
  2=EchoLink:1234567#
  9=Parrot:0123456789# For example, pressing DTMF sequence "D1#" will activate the EchoLink module and connect to the EchoTest conference node.

  Logic Linking
A logic linking configuration section is used to specify information for a link between two or more SvxLink logic cores. Such a link can for example be used to connect a local repeater to a remote repeater using a separate link transceiver. The link is activated/deactivated using DTMF commands and/or automatically depending on your configuration. When the link is active, all audio received by one logic will be transmitted by the other logic(s).

The name of the logic linking section can be chosen freely. In the example configuration file, there is a section [LinkToR4]. To use a logic linking section in a logic core it must be pointed out by the LINKS configuration variable in the GLOBAL section. Example: GLOBAL/LINKS=LinkToR4

CONNECT_LOGICS
    A comma separated list of logic specifications for the logic cores to connect together. Each logic specification has three parts separated by colons: <logic name>:<command>:<announcement name>. The "logic name" is the name of the logic to include in the link. To manually activate or deactivate the link from the just specified logic, "command" is used. The "announcement name" is used when announcing link related activities like activation or deactivation. Both "command" and "announcement name" may be left empty if no manual control is wanted. An example config line may look like this: RepeaterLogic_2m:99:SK3GW,RepeaterLogic_70cm:94:SK3GK It will include two logics in the link, RepeaterLogic_2m and RepeaterLogic_70cm. From the 2m side, the link will be activated when the user send command 991 and deactivated when the user send command 990. Upon activation, an announcement like "activating link to SK3GW" will be played back. From the 70cm side the command will be 941 and 940 respectively. The announcement when activating the link from the 70cm side will be something like "activating link to SK3GK".

DEFAULT_ACTIVE
    The link will be connected automatically during startup of SvxLink if this configuration variable is set to 1. Also, if a link is manually disconnected by a user it will be automatically reconnected after some time of inactivity. The time is specified by setting the TIMEOUT configuration variable. If the TIMEOUT variable is not set, no automatic reactivation will be done.

TIMEOUT
    The number of seconds after which the link will be automatically deactivated if there have been no activity. If 1 have been specified for DEFAULT_ACTIVE, this configuration variable will specify after how many seconds the link will be reactivated after being manually deactivated.

ACTIVATE_ON_ACTIVITY
    Enter a comma separated list of logics, which should automatically activate the link if there is activity (e.g. squelch open, announcements etc) in it. One possible application for this is for example to make the connection of a microphone/speaker combination (without DTMF encoder) for brief announcements but without having to constantly listen in. Example: ACTIVATE_ON_ACTIVITY=MicSpkrLogic

  Local Receiver Section
A local receiver section is used to specify the configuration for a receiver connected to the sound card. In the default configuration file there is a Local configuration section called Rx1. The section name could be anything. It should match the RX configuration variable in the logic core where the receiver is to be used. The available configuration variables are described below.

TYPE
    Always "Local" for a local receiver.

RX_ID
    A single character uniquely identifying this receiver. The RX identity can for example be used in the TCL event scripts to get different roger sounds for different receivers when using a receiver voter.

AUDIO_DEV
    Specify the audio device to use. Normally alsa:plughw:0. Have a look at the AUDIO DEVICE SPECIFICATIONS chapter for more information.

AUDIO_CHANNEL
    Specify the audio channel to use. SvxLink can use the left/right stereo channels as two mono channels. Legal values are 0 or 1.

AUDIO_DEV_KEEP_OPEN
    The normal behaviour for SvxLink is to open an audio device when needed and close it when it does not have to be open anymore. This may cause problems in some applications or with some sound hardware. Set this variable to 1 to force SvxLink to keep the audio device open from application start to exit.

LIMITER_THRESH
    Set the threshold, in dBFS, for the audio limiter. The audio limiter really is a compressor with a very steep compression ratio like 10:1. The limiter is used to help keeping down the audio level for overmodulating stations. For a properly calibrated SvxLink node max FM deviation is -6dBFS. A good value to start with for this parameter is then -6 but try to lower it further (like -9 to -12) if it does not affect audio quality negatively.

SQL_DET
    Specify the type of squelch detector to use. Possible values are: VOX, CTCSS, SERIAL, EVDEV, SIGLEV, PTY, GPIO, GPIOD, HIDRAW or COMBINE. The VOX squelch detector determines if there is a signal present by calculating a mean value of the sound samples. The VOX squelch detector behavior is adjusted with VOX_FILTER_DEPTH and VOX_THRESH. VOX is actually a bit of a misnomer since it's a "Voice Operated Squelch" and VOX actually means "Voice Operated Transmitter". However, the term VOX is widely understood by hams all over the world so we'll stick with it. The CTCSS squelch detector checks for the presence of a tone with the specified frequency. The tone frequency is specified using the CTCSS_FQ config variable. The thresholds are specified using the CTCSS_OPEN_THRESH and CTCSS_CLOSE_THRESH config variables. Other config variables that effect the CTCSS squelch is: CTCSS_MODE, CTCSS_SNR_OFFSETS, CTCSS_BPF_LOW, CTCSS_BPF_HIGH, CTCSS_EMIT_TONE_DETECTED. The SERIAL squelch detector use a pin in a serial port to detect if the squelch is open. This squelch detector can be used if the receiver have an external hardware indicator of when the squelch is open. Specify which serial port/pin to use with SERIAL_PORT and SERIAL_PIN. The EVDEV squelch detector read squelch events from a /dev/input/eventX device. An example where this could be useful is if you have a USB audio device with some buttons on it. Some of these devices generate key press events, much like a keyboard. Specify which /dev/input device node to use using the EVDEV_DEVNAME config variable. Set which events that should open and close the squelch using the EVDEV_OPEN and EVDEV_CLOSE config variables. The GPIO squelch detector read a pin on the GPIO Port. Depending on the level of the pin, the squelch is switched. A HIGH (3.3V) at the pin set the squelch to open and a LOW (GND) level will set the squelch to closed. Specify which squelch pin to use with the GPIO_SQL_PIN configuration variable. On some devices, like the Orange Pi, you also need to set the GPIO_PATH configuration variable. The GPIOD squelch detector read a pin in the GPIO subsystem using the gpiod library. Depending on the level of the pin, the squelch is switched. Set GPIOD interaction up using the following configuration variables: SQL_GPIOD_CHIP, SQL_GPIOD_LINE, SQL_GPIOD_BIAS. The SIGLEV squelch detector use signal level measurements to determine if the squelch is open or not. Which signal level detector to use is determined by the setting of the SIGLEV_DET configuration variable. The open and close thresholds are set using the SQL_SIGLEV_OPEN_THRESH and SQL_SIGLEV_CLOSE_THRESH configuration variables. If using the NOISE signal level detector note the following. The detector is not perfect (it's affected by speech) so you will also want to setup SQL_HANGTIME to prevent it from closing in the middle of a transmission. A value between 100-300ms is probably what you need. If using this squelch type in cooperation with a voter, you'll also probably need to setup SQL_DELAY to get correct signal level measurements. A value of about 40ms seem to be OK. Also, when using the NOISE signal level detector the input audio must be unsquelched since silence will be interpreted as a high signal strength. The PTY squelch expects a very simple protocol over a pseudo-tty device, created by SvxLink at runtime. An 'O' over this pty device indicate an open squelch, a 'Z' is a closed squelch. Define the slave pty using PTY_PATH (e.g. PTY_PATH=/tmp/sql) and SvxLink will create a link to the specified path from it's pseudotty slave device (/dev/pts/X). This can be used by a script to interface custom devices, modems or other hardware to SvxLink. Look for nhrcx.pl or trx_pty_ctrl.py for an example. It is possible to specify the same PTY for multiple functions (e.g. DTMF, ptt etc) in both TX and RX configurations. This may be good if there is one script handling all functions. The HIDRAW squelch supports human interface devices (HID), USB devices like CM108 soundcard e.g. used in the URI Echolink adapter made by DMK. The COMBINE squelch make it possible to combine multiple squelch types using a logical expression. The expression is set up using the SQL_COMBINE configuration variable.

SQL_START_DELAY
    The squelch start delay is of most use when using VOX squelch. For example, if the transceiver makes a noise when the transmitter is turned off, that might trigger the VOX and cause an infinite loop of squelch open/close transmitter on/off. Specify the number of milliseconds that the squelch should be "deaf" after the transmitter has been turned off.

SQL_DELAY
    Specify a delay in milliseconds that a squelch open indication will be delayed. This odd feature can be of use when using a fast squelch detector in combination with the signal level detector. A squelch delay will allow the signal level detector to do its work before an indication of squelch open is sent to the logic core. A delay might be needed when using the voter to choose among multiple receivers. A normal value could be somewhere in between 20-100ms.

SQL_HANGTIME
    How long, in milliseconds, the squelch will stay open after the detector has indicated that it is closed. This configuration variable will affect all squelch detector types. Settable at runtime.

SQL_EXTENDED_HANGTIME
    At low signal strengths it can be beneficial to use a longer squelch hangtime so that it is less likely for the squelch to close. This configuration variable is unset by default. A value of 1000 milliseconds may be a good value to start out with. To enable the extended squelch hangtime feature, set up the SQL_EXTENDED_HANGTIME_THRESH variable. Settable at runtime.

SQL_EXTENDED_HANGTIME_THRESH
    At low signal strengths it can be beneficial to use a longer squelch hangtime so that it is less likely for the squelch to close. This configuration variable is unset by default. When set to a signal level it will activate the extended squelch hangtime feature. When the signal strength during a transmission fall below the set threshold, the extended hangtime will be used. Start out with a value between 10 to 15. The SQL_EXTENDED_HANGTIME variable is used to set how long the extended squelch hangtime should be. Make sure that you have calibrated the signal level detector before turning this feature on. Otherwise it will not work as expected. Settable at runtime.

SQL_TIMEOUT
    Use this configuration variable to set an upper limit, in seconds, for how long the squelch is allowed to be open. If the timeout value is exceeded the squelch is forced to closed. If the squelch close for real, everything is back to normal. When it opens the next time a squelch open will be signaled. For example, use this feature to make sure that a faulty receiver cannot block the system indefinitely.

VOX_FILTER_DEPTH
    The number of milliseconds to create the mean value over. A small value will make the vox react quicker (<200) and larger values will make it a little bit more sluggish. A small value is often better.

VOX_THRESH
    The threshold that the mean value of the samples must exceed for the squelch to be considered open. It's hard to say what is a good value. Something around 1000 is probably a good value. Set it as low as possible without getting the vox to false trigger.

CTCSS_MODE
    This configuration variable set the CTCSS detection method used. These are the ones to choose from:

    •   0 (Default) Will choose the detection mode that is the default in the software. At the moment this is mode 4, "Overlap+Estimated SNR+Frequency estimation".

    •   1 (Neighbor bins) This detection mode will use three narrow frequency bands (~8Hz) to do the detection. One band is centered around the tone to be detected and then there are one band above and one below the tone. These bands are used to estimate the noise floor. This is the detector that have been used in SvxLink for a long time. It is however rather slow with its detection time of about 450ms. There is no good reason to use this detector anymore but it is kept in case the new detector does not work for some hardware setup.

    •   2 (Estimated SNR) This is a newer detector implementation which have some improvements. The most notable difference is that it is faster. The mean detection time will be around 200ms. This is the default detection mode if not specified. This detector will use a larger passband to estimate the noise floor which make it more stable. The default config use the whole CTCSS passband but this can be customized using the CTCSS_BPF_LOW and CTCSS_BPF_HIGH config variables.

    •   3 (Estimated SNR+Phase) This detector is a bit experimental. It is even faster and more narrow than the other detection modes. The mean detection time will be something like 150ms. The detection bandwidth is very narrow and very sharp so that no adjacent tones will trigger the detector. The price to pay for these improvements is that is it a bit less sensitive.

    •   4 (Overlap+Estimated SNR+Frequency estimation) This is an improvement of the mode 3 detector which use another method for extracting the phase information from the signal. This phase information can be used to calculate an estimation of the tone frequency. The accuracy is like tenths of a Herz. Like the mode 3 detector, this detector is faster and more selective. With its 0.75% frequency tolerance, it will not trigger on adjacent CTCSS tones. However, the "undetect" algorithm does not use the frequency estimation so the squelch may be held open by an adjacent tone if already in active state. One downside is that it is a bit more CPU hungry due to using 75% overlap in the frequency analysis, thus processing each sample three times. The reason to use overlap is that the detector will be faster.

CTCSS_FQ
    If CTCSS (PL,subtone) squelch is used (SQL_DET is set to CTCSS), this config variable sets the frequency of the tone to use. The tone frequency ranges from 67.0 to 254.1 Hz. There actually is nothing that will stop you from setting the frequency to something outside this range but there is no guarantee that it will work. If desired it is possible to specify a comma separated list of tone frequencies in which case the squelch will open on all the tone frequencies. Note that for this feature to work well the receivers frequency response in the CTCSS frequency range (67.0 to 254.1Hz) need to be reasonable flat. When choosing tones, try to select tones that are close to each other. However, selecting tones too close may cause both to trigger. Also do not select tones that are a multiple of another tone since overtones may trigger the wrong one.

CTCSS_OPEN_THRESH
    If CTCSS (PL, subtone) squelch is used (SQL_DET is set to CTCSS), this config variable sets the required tone level to indicate squelch open. The value is some kind of estimated signal to noise dB value. If using CTCSS mode 2, 3 or 4 it is helpful to set up the CTCSS_SNR_OFFSETS config variable. This will make the SNR estimation pretty good. Default threshold is 15dB.

CTCSS_CLOSE_THRESH
    If CTCSS (PL, subtone) squelch is used (SQL_DET is set to CTCSS), this config variable sets the required tone level to indicate squelch close. The value is some kind of estimated signal to noise dB value. If using CTCSS mode 2, 3 or 4 it is helpful to set up the CTCSS_SNR_OFFSETS config variable. This will make the SNR estimation pretty good. Default threshold is 9dB.

CTCSS_SNR_OFFSET
    This configuration variable should not be used unless you know why you use it. Using CTCSS_SNR_OFFSETS is often more appropriate.

CTCSS_SNR_OFFSETS
    This config variable is used when CTCSS_MODE is set to 0, 2, 3 or 4. It will adjust the estimated SNR values so that they become very close to a real SNR value. This value will have to be adjusted if CTCSS_FQ, CTCSS_MODE, CTCSS_BPF_LOW or CTCSS_BPF_HIGH changes. Use the siglevdetcal utility to find out what to set this config variable to. There is no requirement to set this config variable up. The downside is that you will then need to experiment more with the CTCSS_OPEN_THRESH and CTCSS_CLOSE_THRESH config variables to find the correct squelch level. If using multiple CTCSS frequencies it may not be possible to find good threshold values due to uneven frequency characteristics for the receiver. The format for this config variable is a comma separated list of frequency:offset pairs. The CTCSS_SNR_OFFSET variable may be used as a form of fallback value that is used if a specific tone frequency in use is missing from this list.

CTCSS_BPF_LOW
    When CTCSS_MODE is set to 0, 2, 3 or 4, this config variable will set the low cutoff frequency for the passband filter. It normally should not have to be adjusted but could improve the detector if some interference falls within the passband (e.g. mains hum). Note however that the more narrow you make the passband, the less stable the detector will be. You may need to compensate by increasing the open/close thresholds or by setting up SQL_DELAY and SQL_HANGTIME. Default is 60Hz.

CTCSS_BPF_HIGH
    When CTCSS_MODE is set to 0, 2, 3 or 4, this config variable will set the high cutoff frequency for the passband filter. It normally should not have to be adjusted but could improve the detector if some interference falls within the passband. Note however that the more narrow you make the passband, the less stable the detector will be. You may need to compensate by increasing the open/close thresholds or by setting up SQL_DELAY and SQL_HANGTIME. Default is 270Hz.

CTCSS_EMIT_TONE_DETECTED
    This configuration variable defaults to 1 which mean that a tone detected signal is emitted when a CTCSS tone is detected. This is required for the function of other features in SvxLink like CTCSS_TO_TG and OPEN_ON_CTCSS. In some situations it may be necessary to disable this behavior, like when using advanced squelch configurations where some tones are actively blocked due to nearby interference.

CTCSS_DEBUG
    Set this to 1 to enable continuously printing SNR values for the CTCSS tone measurements. This is only meant to be activated temporarily while searching for a problem or for initial adjustment.

SERIAL_PORT
    If SQL_DET is set to SERIAL, this config variable determines which serial port should be used for hardware squelch input (COS - Carrier Operated Squelch). Note: If the same serial port is used for the PTT, make sure you specify exactly the same device name. Otherwise the RX and TX will not be able to share the port. Example: SQL_PORT=/dev/ttyS0

SERIAL_PIN
    If SQL_DET is set to SERIAL, this config variable determines which pin in the serial port that should be used for hardware squelch input (COS - Carrier Operated Squelch). It is possible to use the DCD, CTS, DSR or RI pin. If inverted operation is desired, prefix the pin name with an exclamation mark (!). Example: SQL_PIN=!CTS

SERIAL_SET_PINS
    Set the specified serial port pins to a static state. This can be good if using a pin for reference voltage or if a pin have to be in a certain state to not interfere with the operation of some equipment. There are two pins that are possible to use, RTS and DTR. If prefixed with an exclamation mark (!), the pin will be cleared and if not it will be set. Example: SERIAL_SET_PINS=RTS!DTR will set RTS and clear DTR.

EVDEV_DEVNAME
    Specify which /dev/input device node to use for the EVDEV squelch detector. To find out which device node and event codes to use, install the evtest utility. Find a candidate device node under /dev/input/ or /dev/input/by-id/ and try the evtest utility on it. Press some keys on the device you want to read events from. If you're in luck, events will be printed on the screen.

EVDEV_OPEN
    Use the evtest utility, as described above, to find out type, code and value for the event you want to use to open the squelch. For example if type is 1, code is 163 and value is 1, set this config variable to 1,163,1.

EVDEV_CLOSE
    Use the evtest utility, as described above, to find out type, code and value for the event you want to use to close the squelch. For example if type is 1, code is 163 and value is 0, set this config variable to 1,163,0. If you set the same type,code,value combination for both EVDEV_OPEN and EVDEV_CLOSE, that event will toggle the squelch.

GPIO_PATH
    Use this configuration variable to set the path to the sys control devices for GPIO. This normally is /sys/class/gpio but on some hardware, like the Orange Pi, the path is /sys/class/gpio_sw.

GPIO_SQL_PIN
    If SQL_DET is set to GPIO this configuration variable is used to choose which GPIO pin to use for squelch input. The most common name is gpio<number>, like gpio4. Some GPIO drivers use more complex names, like gpio33_pe11. If inverted operation is desired, prefix the pin name with an exclamation mark (!). Example: GPIO_SQL_PIN=!gpio4

SQL_GPIOD_CHIP
    The GPIO chip to use for squelch. The application tries to figure out whether the value is the path to the GPIO chip, its name, label or number. Example: SQL_GPIOD_CHIP=gpiochip0

SQL_GPIOD_LINE
    If GPIOD was specified in SQL_DET, set this config variable to the gpiod line of the GPIO pin to use. If a number is specified it is assumed to be the GPIO pin offset within the chip. If a pin name is specified SvxLink will try to find a pin with that name within the chip. Normally, the pin will be active high but if the pin specification is prefixed with an exclamation mark it will be active low instead. For some hardware platforms you may need to also set the SQL_GPIOD_CHIP configuration variable, if the pin you want to use is not on the default GPIO chip. Example: SQL_GPIOD_LINE=17

SQL_GPIOD_BIAS
    This config variable is only available when SvxLink has been built with libgpiod >= 1.5. It makes it possible to set if the squelch GPIO pin should be pulled up or down. If you don't know what that mean you should check the documentation for your hardware interface, whether it require a pull up or down. It's an electronics thing. In essence, a pull up will force the pin high if nothing is connected to it and a pull down will force it low.

SQL_COMBINE
    This configuration variable is used to set a logical expression that is used to combine multiple squelch types. The expression syntax consist of names for configuration file sections where a specific squelch type is set up and of the operators '| (logical or), '&' (logical and) and '!' (logical negation). Parts of the expression may be grouped by surrounding them with parentheses, effectively changing operator precedence. The normal precedence is that '&' bind harder to its operands than '|'. The '!' operator bind hardest. Below is a simple example of how to set up a combined squelch.
      [Rx1:CTCSS]
      SQL_DET=CTCSS
      CTCSS_FQ=77.0
      CTCSS_SNR_OFFSETS=77.0:-3.22
      [Rx1:SIGLEV]
      SQL_DET=SIGLEV
      SQL_SIGLEV_RX_NAME=Rx1
      SQL_SIGLEV_OPEN_THRESH=30
      SQL_SIGLEV_CLOSE_THRESH=2
      [Rx1]
      ...
      SQL_DET=COMBINE
      SQL_COMBINE=Rx1:CTCSS | Rx1:SIGLEV
      ... The configuration section names used above is just a convention but it is wise to include the name of the associated RX for better diagnostic messages. Squelch timing parameters like SQL_DELAY, SQL_HANGTIME etc may be set up in the receiver configuration section (Rx1 above). The parameters will not be applied to each subsquelch but rather to the combiner itself. It is often better to set up parameters in each squelch specific configuration section unless you really know what you are doing.

SQL_SIGLEV_RX_NAME
    When using the SIGLEV squelch type, specify the name of the receiver that provide the signal level. This is only useful when the squelch configuration is not in the same configuration section as the receiver, like when using the COMBINE squelch type. The default is to use the same configuration section as where the SIGLEV squelch is configured.

SIGLEV_DET
    Choose which type of signal level detector to use. The available choices are: "NONE", "NOISE" (default), "TONE", "AFSK", "SIM" or "CONST". Depending on other configuration there may be more choices available. For example, if a Ddr receiver is used there will also be a DDR signal level detector available. The signal level detector is only needed when using multiple receivers in a voter configuration or when using the SIGLEV squelch type. Type NONE disable the signal level detector. This may be used if no signal level detector is needed. Type NOISE use a bandpass filter in the range of 5 - 5.5kHz (CARD_SAMPLE_RATE >= 16000) or a high-pass filter at 3.5kHz (CARD_SAMPLE_RATE = 8000) to estimate the amount of noise present on the signal. If the passband contain a small amount of energy, a strong signal is assumed. If the passband contain more energy, a weaker signal is assumed. The noise detector must be calibrated for the receiver and audio levels you use. This is done using the SIGLEV_SLOPE and SIGLEV_OFFSET configuration variables. See chapter CALIBRATING THE SIGNAL LEVEL DETECTOR below for more information. Type TONE is not really a signal level detector but rather a transport mechanism for getting signal level measurements from a remote receiver site, linked in via RF, to the main SvxLink site. It is using ten tones, one for each signal level step, in the high audio frequency spectrum (5.5 - 6.4kHz, 100Hz step) to indicate one of ten signal levels. Only the receiving part have been implemented in SvxLink at the moment. On the remote receiver side an Atmel AVR ATmega8 is used to map the signal level voltage to tone frequencies. Use the TONE_SIGLEV_MAP configuration variable to map each tone to a corresponding signal level value in between 0 - 100. Type AFSK is like the TONE detector really a transport mechanism. Signal level values are transmitted using Audio Frequency Shift Keying, AFSK, over the receiver uplink channel from a remote receiver site. AFSK reception must have been enebled by setting OB_AFSK_ENABLE=1 and also optionally IB_AFSK_ENABLE=1. Type SIM is a simulated signal level detector that can be used to debug problems in the SvxLink software. Use the SIGLEV_MIN, SIGLEV_MAX, SIGLEV_DEFAULT, SIGLEV_TOGGLE_INTERVAL and SIGLEV_RAND_INTERVAL configuration variables to configure the simulator. Type CONST is not a detector at all. Instead it is possible to set a constant signal level. This can be used for audio sources that does not have the concept of a signal level. If configured in a receiver managed by a Voter it can be used to determine priority in comparison to other receivers and audio sources. Use the SIGLEV_CONST configuration variable to set the signal level.

HID_DEVICE
    This parameter defines the device your hidraw adapter is connected to. This port is created by the linux/hidraw driver. e.g. HID_DEVICE=/dev/hidraw3

HID_SQL_PIN
    Define the pin your hardware squelch (from RX) is connected to. Valid values are VOL_UP, VOL_DN, MUTE_PLAY or MUTE_REC. Example: HID_SQL_PIN=VOL_UP

SIGLEV_SLOPE
    The slope (or gain) of the signal level detector. See chapter CALIBRATING THE SIGNAL LEVEL DETECTOR below for more information.

SIGLEV_OFFSET
    The offset of the signal level detector. See chapter CALIBRATING THE SIGNAL LEVEL DETECTOR below for more information.

SIGLEV_BOGUS_THRESH
    This configuration variable set an upper threshold for the estimated signal level when using the noise signal level detector. If the estimation goes over the given threshold, a signal level of 0 will be reported. This can be used as a workaround when using a receiver with squelched audio output. When the squelch is closed, the receiver audio is silent. The signal level estimator will interpret this as a very strong signal. Setting up the bogus signal level threshold will counteract this behavior but a better solution is to use unsquelched audio if possible. By default this feature is disabled. If enabling it, start with a value somewhere around 120.

TONE_SIGLEV_MAP
    This configuration variable is used to map tones to signal level values when SIGLEV_DET=TONE. It is a comma separated list of ten values in the 0 - 100 range. The first value map to the 5500Hz tone, the second to the 5600Hz tone and so on. The last value map to the 6400Hz tone. What levels the tones should be mapped to depends on the tone sender implementation. The default tone map is 10,20,30...,100. The Atmel AVR processor used by the author have a reverse mapping so that the first tone (5500Hz) indicate the highest signal strength and the last tone (6400Hz) indicate the lowest signal strength. It is also not linear since it's more important to have fine measurement granularity in the lower signal strength range. This is how the mapping look for the AVR: 100,84,60,50,37,32,28,23,19,8.

SQL_SIGLEV_OPEN_THRESH
    This is the squelch open threshold for the SIGLEV squelch detector. If using the NOISE signal level detector, make sure to first calibrate the signal level detector using the SIGLEV_SLOPE and SIGLEV_OFFSET configuration variables. The signal level detector should normally be calibrated so that full signal strength is 100 and no signal is 0. Depending on your background noise level a good value for this configuration variable is between 5 and 20.

SQL_SIGLEV_CLOSE_THRESH
    This is the squelch close threshold for the SIGLEV squelch detector. If using the NOISE signal level detector, make sure to first calibrate the signal level detector using the SIGLEV_SLOPE and SIGLEV_OFFSET configuration variables. The signal level detector should normally be calibrated so that full signal strength is 100 and no signal is 0. Depending on your background noise level a good value for this configuration variable is between 1 and 10.

SIGLEV_MIN
    The minimum signal level used by SIM signal level detector.

SIGLEV_MAX
    The maximum signal level used by SIM signal level detector.

SIGLEV_DEFAULT
    The default signal level set on startup by the SIM signal level detector.

SIGLEV_TOGGLE_INTERVAL
    The interval, in milliseconds, that the SIM signal level detector will use to toggle between the maximum and the minimum signal levels.

SIGLEV_RAND_INTERVAL
    The interval, in milliseconds, that the SIM signal level detector will use between randomizing a new signal level value. At each interval, the simulator will randomly either increase or decrease the signal level with one step.

DEEMPHASIS
    Apply a deemphasis filter on received audio. The deemphasis filter is used when taking audio directly from the detector in the receiver, like when using a 9k6 packet radio connector. If not using a deemphasis filter the high frequencies will be amplified resulting in a very bright (tinny) sound.

SQL_TAIL_ELIM
    Squelch tail elimination is used to remove noise from the end of a received transmission. This is of most use when using CTCSS or SIGLEV squelch with unsquelched input audio. A normal value is a couple of hundred milliseconds. Note that the audio will be delayed by the same amount of milliseconds. This does not matter much for a simplex link but for a repeater the delay might be annoying since you risk hearing the end of your own transmission.

PREAMP
    The incoming signal will be amplified by the specified number of dB. This can be used as a last measure if the input audio level can't be set high enough on the analogue side. A value of 6dB will double the signal level. Note that this is a digital amplification. Hence it will reduce the dynamic range of the signal so usage should be avoided if possible. It's always better to correct the audio level before sampling it.

PEAK_METER
    This is a help to adjust the incoming audio level. If enabled it will output a message when distortion occurs. To adjust the audio level, first open the squelch. Then increase the audio level until warning messages are printed. Decrease the audio level until no warning messages are printed. After the adjustment has been done, the peak meter can be disabled. 0=disabled, 1=enabled.

DTMF_DEC_TYPE
    Specify the DTMF decoder type. Set it to INTERNAL to use the internal software DTMF decoder. To use the S54S interface featuring a hardware DTMF decoder, set it to S54S. To control it over a pseudo tty device set it to PTY. Setting it to PTY will install the PTY dtmf decoder. SvxLink creates a symlink linked to a slave pty device on runtime. The name has to be defined with DTMF_PTY. If AFSK reception is enabled using OB_AFSK_ENABLE/IB_AFSK_ENABLE, remotely decoded DTMF digits may be received by setting this configuration variable to AFSK. NONE or commenting it out will disable DTMF detection.

DTMF_MUTING
    Mute the audio during the time when a DTMF digit is being received. Note that the audio will be delayed like 40-75ms, depending on the DTMF decoder used, to give the decoder time to do its work. This does not matter much on a simplex link but on a repeater it could be annoying since you will hear the last 40-75 milliseconds of your own transmission. To counteract the added delay one can set up the SQL_TAIL_ELIM configuration variable to at least 40 milliseconds. Legal values for DTMF_MUTING are 0=disabled, 1=enabled.

DTMF_HANGTIME
    This configuration variable can be used if the DTMF decoder is too quick to indicate digit idle. That does not matter at high signal strengths but for weaker signals and mobile flutter it's not good at all. Each DTMF digit will be detected multiple times. Using this configuration variable, the time (ms) a tone must be missing to be indicated as off can be extended. Setting this value too high will cause the decoder to be a bit sluggish and it might consider two digits as one. The hang time only affect consecutive digits of the same value (e.g. 1 1). If a detected digit differs from the previously detected digit (e.g 1 2), the hang time is immediately canceled and the detected digit is considered as a new one. A good default value is 50-100ms.

DTMF_SERIAL
    When using an external hardware DTMF decoder this config variable is used to specify a serial port (e.g. /dev/ttyS0).

DTMF_PTY
    When using the PTY DTMF "decoder" this configuration variable will set the path to the PTY slave softlink that the external interface script use to communicate to SvxLink. Over this softlink a very simple communication protocol is used to notify SvxLink about received DTMF digits: 0-9, A-F, *, #. "E" is the same as "*" and "F" is the same as "#". Sending a digit tell SvxLink when it starts. To tell SvxLink that the digit has ended, send a space character. The PTY DTMF "decoder" can be used by an external script to interface custom devices, modems or other hardware to SvxLink. Look for nhrcx.pl or trx_pty_ctrl.py for an example. It is possible to specify the same PTY for multiple functions (e.g. squelch, ptt etc) in both TX and RX configurations. This may be good if there is one script handling all functions. Example: /tmp/rx1_dtmf.

DTMF_MAX_FWD_TWIST
    DTMF use two tones to encode digits 0-9, A-F. These two tones should normally have the sample amplitude. The difference in amplitude is called twist. Forward twist is when the higher frequency tone is lower in amplitude than the lower frequency tone. According to the standards, 8dB forward twist should be allowed. Some transmitters do not correctly modulate the DTMF tones to get zero twist. The most common situation is that the forward twist is too large. Increasing this configuration variable above 8dB might allow DTMF from these transmitters to be detected. When doing this, the DTMF detector will be more sensitive to noise and might cause more false triggers.

DTMF_MAX_REV_TWIST
    DTMF use two tones to encode digits 0-9, A-F. These two tones should normally have the sample amplitude. The difference in amplitude is called twist. Reverse twist is when the lower frequency tone is lower in amplitude than the higher frequency tone. According to the standards, 4dB reverse twist should be allowed but SvxLink will allow 6dB by default. The most common reason for getting reverse twist is a bad de-emphasis filter or that none at all is used, like when taking audio directly from the FM discriminator. Have a look at the DEEMPHASIS configuration variable before starting to modify this configuration variable.

DTMF_DEBUG
    Set to 1 to continuously print software DTMF decoder decision parameters. This should only be used for a short while to pinpoint problems with the DTMF decoding since it will print one row of analysis parameters 100 times per second. The following parameters are printed.

    •   pwr - The power in the audio signal. Must be over about -50dB.

    •   q - Quality. Should be close to 1.00 for a good detection. If the signal is strong but the value is low anyway, the signal probably is distorted for some reason. The input audio level may be too high for example.

    •   twist - The amplitude difference between the two tones. Should be around 0dB, which means the tones should ideally be of the same strength. By default, values between -6dB to +8dB are accepted but the thresholds can be set using the DTMF_MAX_FWD_TWIST and DTMF_MAX_REV_TWIST configuration variables.

    •   rowq - Quality of the row (low group) tone. Should be close to one.

    •   colq - Quality of the column (high group) tone. Should be close to one.

    •   digit - The digit mapped to the two detected tones.

    •   row3rd - The row tone relation to its third overtone. Should be close to zero. If it's not, the signal is probably distorted.

    •   col3rd - The column tone relation to its third overtone. Should be close to zero. If it's not, the signal is probably distorted.

    •   im - The relation of the two tones to their intermodulation product. Should be close to zero. If it's not, the signal is probably distorted.

1750_MUTING
    Mute the audio during a call tone of 1750Hz is received. Note that the audio will be delayed 75ms to give the tone detector time to do its work. This does not matter much on a simplex link but on a repeater it could be annoying since you will hear the last 75 milliseconds of your own transmission. To counteract the added delay one can set up the SQL_TAIL_ELIM configuration variable to at least 75 milliseconds. Legal values for 1750_MUTING are 0=disabled, 1=enabled.

SEL5_TYPE
    Define here your selective tone call system. You have the choice of the following types: ZVEI1, ZVEI2, ZVEI3, PZVEI, PDZVEI, DZVEI, CCITT, EEA, CCIR1, CCIR2, NATEL, EURO, VDEW, AUTO-A, MODAT, PCCIR and EIA. Only one system can be used at the same time. Please take into consideration that some Sel5 standards are using the same or similar tones so it may have some unwanted effects if you define ZVEI1 for SvxLink and a (e.g.) ZVEI3 sequence is received.

SEL5_DEC_TYPE
    At the moment only SEL5_DEC_TYPE=INTERNAL is valid. Maybe we have support for some external tone detectors later. To disable SEL5 tone decoding, specify NONE or just comment the configuration variable out.

RAW_AUDIO_UDP_DEST
    Setting this configuration variable makes it possible to stream the raw audio from the sound device to an UDP socket. The sample format is the one used internally in SvxLink, that is each sample is represented by a 32 bit float. The sample rate is the same as the one chosen for the audio device. The destination is specified as ip-address:port. Example: RAW_AUDIO_UDP_DEST=127.0.0.1:10000

OB_AFSK_ENABLE
    Set to 1 to enable reception of metadata like signal level measurements, DTMF digits and tone detections via out-of-band (OB) AFSK. The out-of-band AFSK is transmitted above the voice band so that it is possible to transmit AFSK bursts at the same time as someone is speaking. The AFSK bursts are filtered out before the audio is handed on to the next stage so normal users should never hear the AFSK bursts. The AFSK feature is typically used on a remote receiver uplink. The protocol used is SvxLink specific. Data is transmitted in 300Bd with a shift of 170Hz and a center frequency of 5500Hz. The RemoteTrx application have the capability to transmit this protocol.

OB_AFSK_VOICE_GAIN
    To be able to send both voice and AFSK at the same time it may be necessary to lower the level of the voice audio as to not overdrive the transmitter. This is compensated in the link receiver by amplifying the voice audio back to its original level. This configuration variable should thus be set to the negated value of the same configuration variable in the transmitter section of the transmitting RemoteTrx. If it's set to -6dB in the transmitter configuration it should be set to 6dB here.

IB_AFSK_ENABLE
    Set to 1 to enable reception of an initial signal level measurement via in-band (IB) AFSK. This is used in cooperation with the out-of-band AFSK feature to quickly transfer a signal level measurement to get the squelch opened. The in-band AFSK is transmitted in the voice band and can thus use the higher baudrate of 1200Bd. Since it's only transmitted when the squelch is closed the end user will not hear the AFSK burst. The AFSK feature is typically used on a remote receiver uplink. The protocol used is SvxLink specific. Data is transmitted in 1200Bd with a shift of 1000Hz and a center frequency of 1700Hz. The RemoteTrx application have the capability to transmit this protocol.

CTRL_PTY
    Set this configuration variable to the path of a PTY to use for controlling a receivers frequency and modulation. This can be used to interface a receiver to SvxLink using a translation script, like trx_pty_ctrl.py. To set the receive frequency, SvxLink will send the sequence "f<frequency>;". The frequency will be in Hz, e.g. f145550000; will be sent to set the receiver to 145.550MHz. To set the modulation the command is "m<modulation>;". Look at the documentation of the MODULATION configuration variable to see which modulations that are available. To set "normal" 25kHz channel spaced FM the command would be mFM;. It is possible to specify the same PTY for multiple functions (e.g. squelch, ptt etc) in both TX and RX configurations. This may be good if there is one script handling all functions.

LADSPA_PLUGINS
    Used to set up one or more LADSPA plugins to process the received audio. The processing chain is applied just before the final stages of the receiver audio processing and will only affect how the audio sounds. Any digital signal processing done on the audio before that, like DTMF, CTCSS etc, is unaffected. See "LADSPA PLUGIN USAGE" for more information.

  Ddr Receiver Section
A special kind of local receiver is the Digital Drop Receiver (DDR). It will use either the rtl_tcp utility or a direct USB connection to interface to a RTL2832U based DVB-T USB dongle and use that as a wide-band receiver. These USB dongles can be bought cheaply from an Internet shop (~$10). The radio performance may not be great but better than one might think. Usage as a cheap local coverage receiver or as a link receiver may work very well. One big advantage of using a wide-band receiver is that it is possible to monitor more than one narrow band channel at a time. The only limit is the CPU power and the bandwidth of the wide-band tuner. You probably need a Pentium4 or better to fulfill the CPU demands. Getting the DVB-T dongle running is out of scope for this document but what you absolutely need to do is to find out the frequency error on your specific dongle. When you have figured out what the frequency error is, set up the FQ_CORR configuration variable in the wide-band receiver configuration section. The rtl_tcp utility is in a package named similar to something like rtl-sdr. When you have the rtl-sdr stuff installed, just start rtl_tcp. No command line arguments are needed. Then configure a Ddr receiver in SvxLink. All configuration variables that are available for an ordinary local receiver is also available for a Ddr receiver, except the audio device related ones which are just ignored. The following configuration variables are available in addition to the ordinary ones.

FQ  The narrow-band channel frequency to tune to.

MODULATION
    The modulation used on the channel. Legal values are: "FM" (two-way radio frequency modulation), "NBFM" (two-way radio narrow frequency modulation), "WBFM" (broadcast wide-band frequency modulation), "AM" (two-way radio amplitude modulation), "NBAM" (two-way radio narrow band amplitude modulation), "USB" (Upper Sideband), "LSB" (Lower Sideband), "CW" (Continuous Wave, e.g. Morse), "WBCW" (CW wide).

WBRX
    The configuration section for the wide-band receiver to connect this DDR to. See "wide-band Receiver Section" below.

SIGLEV_DET
    For a Ddr there also is a special signal level detector available, DDR, that will measure the RF power before demodulation. This is much more reliable than estimating the signal power through the audio which is normally done in SvxLink. The drawback is that the Ddr signal level is not completely comparable to the ordinary SvxLink signal level measurements since it have a larger dynamic range. Set SIGLEV_DET=DDR to activate the Ddr signal level detector.

  Wide-band Receiver Section
A wide-band receiver section is used to configure access to a wide-band receiver which can be used by a Digital Drop Receiver (DDR), described above, to handle multiple narrow-band channels using the same hardware. The only hardware supported at the moment is RTL2832U based DVB-T USB dongles. SvxLink access the dongle directly via USB or through the rtl_tcp utility, which make the dongle available on a TCP network port. The following configuration variables are available:

TYPE
    The type of wide-band receiver used. The only supported values right now are "RtlTcp" and "RtlUsb".

DEV_MATCH
    When using RtlUsb, this configuration variable is used to select the dongle to use if there are multiple dongles connected to the computer. When looking for dongles, SvxLink will try to match the string given in this configuration variable in different ways. First, if it's a digit, a match against the device index is tried. The device index is just a number, zero and up, that is given to a dongle when it's inserted. If the device index does not match, a match against the beginning, end or the whole serial number will be tried. Default: 0 (first device found)

HOST
    The name of the host that the rtl_tcp utility is running on (Default: localhost).

PORT
    The TCP port that rtl_tcp is listening on (Default: 1234).

SAMPLE_RATE
    The sample rate used by the dongle. Legal values are 960000 and 2400000 (Default: 960000).

FQ_CORR
    This is probably the most important configuration variable. Most dongles are far off in frequency so they need to be calibrated. Calibrating the dongle can be done in multiple ways. The recommended way is to use the devcal utility that is distributed along with SvxLink. The calibration procedure is described in the devcal (1) manual page. The end result should be a correction value for how far off the dongle is in frequency counted in parts per million (PPM). That is, how many Hz per MHz is the tuner off by. Typical values are in the range -100 to 100.

CENTER_FQ
    The frequency, in Hz, that the wide-band tuner should be placed at. This configuration variable should normally be left unset since SvxLink will try to place the wide-band tuner to cover all set up Ddr frequencies. SvxLink will also try to avoid placing a Ddr on the center frequency of the wide-band spectrum since there is usually some noise there. Only use this configuration variable if you need to override the automatic placement for some reason.

XVRTR_OFFSET
    If a transverter is used, this configuration variable can be set to the frequency offset that the transverter introduce. The frequency set here will be added to the center frequency of the wide-band receiver.

GAIN
    If unset, automatic gain is used. Do not use automatic gain control if using the DDR signal level detector. That may mess up the measurements. Finding a good gain setting may be hard. Too little and you will not hear the signals you want to hear. Too much and the tuner will be driven into distortion. One way to decide the maximum usable gain is to use the PEAK_METER explained below. When there are no distortion warning messages printed or just a single one now and then you have found the max gain. You should probably back at least one step down from this value. If the signals you want to receive are very strong, set the gain as low as possible. What gain values that are available is tuner dependent. SvxLink will print the available gain values when it establishes the connection to the tuner. Typical values are in the range -10 to 50dB.

PEAK_METER
    If PEAK_METER is set to 1, a warning will be printed every time the tuner is driven into distortion. If it happens too often the gain should be lowered. At most, one warning per second will be printed.

  LocalSim Receiver Section
A simulated local receiver can be used to debug problems in the SvxLink software. The only thing that this very simple simulator does is to play a tone. The generated tone can be controlled using some configuration variables.

SIM_WAVEFORM
    Set the waveform to use; SIN=sine wave, SQUARE=square wave.

SIM_TONE_FQ
    Set the frequency of the tone in Hz.

SIM_TONE_PWR
    Set the tone power in dB. 0dB corresponds to the power in a full-scale sine wave.

  Voter Section
Receiver type "Voter" is a "receiver" that combines multiple receivers and selects one of them to take audio from when the squelch opens. Which receiver to use is selected directly after squelch open. It is possible to set up a voting delay which will make the voter wait a while before choosing which RX to use. This will give all receivers some time to report their signal strengths. After the initial choice have been made a periodic check is done to see if any of the other receivers receive a stronger signal. In the default configuration file there is a voter section called Voter.

TYPE
    Always "Voter" for a voter.

RECEIVERS
    Specify a comma separated list of receivers that the voter should use. Optionally the receiver name may be followed by a colon and a squelch delay value. This can be used to adjust the voting delay for receivers that always are slower to open for some reason. The delay value given will be subtracted from the voting delay if the receiver is the first one to open. The usage of the delay value is best illustrated with an example. Let's say we have three receivers where two of the receivers take at most 100ms to report signal level and one receiver requires 300ms. We then need to set the VOTING_DELAY to something like 350ms so as to be sure that all receivers get a chance to report their signal level measurement. If only the slow receiver opens there will be a total delay of 300+350=650ms. This is unnecessarily long since the other two receivers should have reported their signal strength way earlier. It's thus safe to shorten the voting delay for the slow receiver, so we do this: RECEIVERS=FastRx1,FastRx2,SlowRx:200. The total squelch open delay will now be 100+350=450ms for the fast receivers and 300+350-200=450ms for the slow receiver. That is, all receivers are now equally fast. Example: RECEIVERS=Rx1,Rx2:200,Rx3

VOTING_DELAY
    Specify the delay in milliseconds that the voter will wait after the first squelch open detection until the decision of which receiver to use is made. This time must be set sufficiently high to allow all receivers to calculate and report the signal level. Incoming audio and DTMF digits will be buffered for all receivers during the delay time so nothing will be lost, but of course the audio will be delayed the specified amount of time. This is most noticeable when using a repeater logic. Use the BUFFER_LENGTH configuration variable to adjust the buffer length. The default voting delay is 0.

BUFFER_LENGTH
    Use this configuration variable to adjust the length of the voting delay buffer. If not specified, the buffer length will be the same as the voting delay. When using the voter with a repeater logic, try to keep this variable at 0 to reduce the latency. Only increase it if you feel audio is lost in the beginning of transmissions.

REVOTE_INTERVAL
    This is the interval time in milliseconds with which the voter will check if another receiver is receiving a stronger signal. If that is the case, a receiver switch will be initiated. Default is 1000 milliseconds.

HYSTERESIS
    The hysteresis setting will prevent the voter from switching back and forth between two receivers that are equal in signal strength. For a switch to occur, the other receivers signal strength must exceed the current receivers signal strength by the percent specified in this configuration variable. So if the hysteresis is set to 50% and the received signal strength on the current receiver is 40, a signal strength of 40*1.5=60 is required on another receiver to initiate a switch. At squelch open, if the received signal strength plus hysteresis is larger than 100, the voting delay will be skipped. The default hysteresis is 50 percent.

RX_SWITCH_DELAY
    When a receiver switch is initiated by the voter, it will wait the number of milliseconds specified in this configuration variable before actually performing the switch. The switch will only occur if the other receivers signal strength is still higher. Default is 500 milliseconds.

SQL_CLOSE_REVOTE_DELAY
    The voter will wait the number of milliseconds specified in this config variable after a squelch close before voting in another receiver. There are two reasons for using this delay. The first is to prevent the voter from going into idle state immediately when the squelch close for a fluttery signal. If it goes to idle, the procedure with voting delay may cause longer dropouts than necessary. The second reason to use this config variable is if different receivers have different hang times (explicitly or implicitly). If both a slow and fast receiver is receiving the same signal and the faster is currently chosen, when the PTT is released the slower receiver will be voted before closing. This will cause a double squelch tail and double roger beep. Default is 500 milliseconds.

COMMAND_PTY
    Specify the path to a PTY that can be used to control the voter from the operating system. Available commands:

    •   ENABLE rx_name - Enable the given receiver

    •   MUTE rx_name - Mute the given receiver

    •   DISABLE rx_name - Disable the given receiver

    The difference between MUTE and DISABLE is that in the mute state only the content (audio, dtmf, selcall tone detectors etc) is muted but the receiver is still operational. That is probably only useful if also setting VERBOSE=1 so that squelch open/close can be monitored in the log. That may be useful if a new receiver is connected to the system which you want to monitor for a while without having it actually participate in the voting. It may also be of use if a receiver misbehaves in which case it can be monitored until it stops misbehaving. Commands can be issued using a simple echo command from the shell. Example: echo "DISABLE Rx1" >/dev/shm/voter_ctrl

VERBOSE
    Set this to 1 to enable verbose mode. In verbose mode the squelch state events of the satellite receivers will be printed. This can be used for fine tuning voter timing parameters. Default: 0 (disabled)

  Networked Receiver Section
A networked receiver section is used to specify the configuration for a receiver connected through a TCP/IP network. In the default configuration file there is a networked receiver configuration section called NetRx. The section name could be anything. It should match the RX configuration variable in the logic core where the receiver is to be used. The available configuration variables are described below. How to use a networked receiver is further described in the remotetrx(1) manual page.

TYPE
    Always "Net" for a networked receiver.

HOST
    The hostname or IP address of the remote receiver host.

TCP_PORT
    The TCP port that RemoteTrx listen on. The default is 5210.

LOG_DISCONNECTS_ONCE
    Set this configuration variable to 1 to suppress logging of multiple disconnect messages in a row, like when there is no RemoteTrx running on the other side. Thus, failed reconnect attempts will not be logged at all. This may be of use if a RemoteTrx is missing for a long time or if it's only used from time to time. The default is 0 which means that all reconnect attempts will be logged.

AUTH_KEY
    This is the authentication key (password) to use to connect to the RemoteTrx server. The same key have to be specified in the RemoteTrx configuration. If no key is specified in the RemoteTrx config, the login will be unauthenticated. A good authentication key should be 20 characters long. If the same RemoteTrx is used for both RX and TX, the same key must be specified in the RX as well as in the TX configuration section. The key will never be transmitted over the network. A HMAC-SHA1 challenge-response procedure will be used for authentication.

CODEC
    The audio codec to use when transferring audio from this remote receiver. Available codecs are: RAW (512kbps), S16 (256kbps), GSM (13.2kbps), SPEEX (8-25kbps), OPUS (8-64kbps). These are raw bit-rate values. There will be some overhead added to this so the real bit-rates on the wire are a little bit higher. The OPUS codec is the most modern one and it also have the best quality for a given bit-rate.

SPEEX_ENC_FRAMES_PER_PACKET
    Speex encoder setting. Each Speex frame contains 20ms audio. If using a low bit-rate configuration, the network overhead will be quite noticeable if sending each frame in its own packet. One way to lower the overhead is to send multiple frames in each network packet. The drawback with doing this is that you get more delay. If setting this option to something like 4 (default), the delay will be about 4x20=80ms.

SPEEX_ENC_QUALITY
    Speex encoder setting. Specify the encoder quality using a number between 0-10. Lower values give poorer quality and lower bit-rates.

SPEEX_ENC_BITRATE
    Speex encoder setting. Specify the bit-rate to use. Speex will snap to the nearest lower possible bit-rate. Possible values range from 2150 to 24600 bps. You should probably not specify quality at the same time as bit-rate. Not sure though...

SPEEX_ENC_COMPLEXITY
    Speex encoder setting. The complexity setting (0-10) tells the encoder how much CPU time it should spend on doing a good job. The difference in SNR between the lowest and highest value is about 2dB. Set it as high as possible without overloading the CPU on the encoding computer (check CPU usage using command "top").

SPEEX_ENC_VBR
    Speex encoder setting. Enable (1) or disable (0) variable bit-rate encoding. If enabled, the encoder will try to keep a constant quality by increasing the bit-rate when needed.

SPEEX_ENC_VBR_QUALITY
    Speex encoder setting. The quality (0-10) to use in variable bit-rate mode.

SPEEX_ENC_ABR
    Speex encoder setting. The average bit-rate encoding will try to keep a target bit-rate by continuously adjusting the quality. This configuration variable specify the target bit-rate and enable ABR. It also need to have VBR enabled so don't force it to off.

SPEEX_DEC_ENHANCER
    Speex decoder setting. Enable (1) or disable (0) the perceptual enhancer in the decoder. Perceptual enhancement is a part of the decoder which, when turned on, attempts to reduce the perception of the noise/distortion produced by the encoding/decoding process. In most cases, perceptual enhancement brings the sound further from the original objectively (e.g. considering only SNR), but in the end it still sounds better (subjective improvement).

OPUS_ENC_FRAME_SIZE
    Opus encoder setting. Specify how large, in milliseconds, each audio packet should be. Default: 20ms.

OPUS_ENC_COMPLEXITY
    Opus encoder setting. The complexity setting (0-10) tells the encoder how much CPU time it should spend on doing a good job. Set it as high as possible without overloading the CPU on the encoding computer (check CPU usage using command "top"). Default: 10.

OPUS_ENC_BITRATE
    Opus encoder setting. This is the bit-rate that the encoder will encode for. Rates from about 8000 to 64000 bits per second are meaningful but the codec can handle from like 2500 to 512000 bps. Default: 20000bps.

OPUS_ENC_VBR
    Opus encoder setting. Enable (1) or disable (0) variable bit-rate encoding. If enabled, the encoder will try to keep a constant quality by increasing the bit-rate when needed and decrease it when the quality can be assured with a lower bit-rate. The target average bit-rate is the one set by OPUS_ENC_BITRATE. Default: 1.

  Local Transmitter Section
A local transmitter section is used to specify the configuration for a local transmitter. In the default configuration file there is a configuration section called Tx1. The section name could be anything. It should match the TX configuration variable in the logic core where the transmitter is to be used. The available configuration variables are described below.

TYPE
    Always "Local" for a local transmitter.

TX_ID
    A single character ident for this transmitter. It is for example used in state events published by transmitters through a STATE_PTY or other state event consumers within SvxLink.

AUDIO_DEV
    Specify the audio device to use. Normally alsa:plughw:0. Have a look at the AUDIO DEVICE SPECIFICATIONS chapter for more information.

AUDIO_CHANNEL
    Specify the audio channel to use. SvxLink can use the left/right stereo channels as two mono channels. Legal values are 0 or 1.

AUDIO_DEV_KEEP_OPEN
    The normal behaviour for SvxLink is to open an audio device when needed and close it when it does not have to be open anymore. This may cause problems in some applications or with some sound hardware. Set this variable to 1 to force SvxLink to keep the audio device open from application start to exit.

LIMITER_THRESH
    Set the threshold, in dBFS, for the audio limiter. The audio limiter really is a compressor with a very steep compression ratio like 10:1. The limiter is used to help keeping down the audio level to not overmodulate the transmitter. For a properly calibrated SvxLink node max FM deviation is -6dBFS. A good value to start with for this parameter is then -6 but try to lower it further (like -9 to -12) if it does not affect audio quality negatively.

PTT_TYPE
    Use this configuration variable to specify which type of hardware to use to control the PTT. Specify "SerialPin" for using a pin in the serial port, "GPIO" (sysfs=deprecated)/"GPIOD" to use a pin in a GPIO port, "PTY" if you want to use an external interface script via a pseudo tty port or "Hidraw" to use the linux/hidraw driver to support hidraw devices like CM108 sound card, e.g. URI device from DMK. Set PTT_TYPE to "Dummy" or "NONE" to not use any PTT hardware at all. It is an error to not specify PTT_TYPE. Use PTT_PIN to specify the pin to use for "SerialPin" or "GPIO", Use PTT_GPIOD_LINE and PTT_GPIOD_CHIP to specify the GPIO pin to use for "GPIOD".

PTT_PORT
    Specify the serial port that the PTT is connected to. E.g. /dev/ttyS0 for COM1.

PTT_PIN
    If PTT_TYPE is set to "SerialPin", specify the pin(s) in the serial port that the PTT is connected to. It is possible to specify one or two serial port pins. Some interface boards require that you specify two pins since one pin does not provide enough drive power to the circuit. A "!" in front of the pin name indicates inverted operation. Some of the possible values are RTS, DTRRTS, !DTR!RTS or even DTR!RTS. If GPIO was specified in PTT_TYPE, set the PTT_PIN config variable to the pin name of the GPIO-pin to use. The most common name is gpio<number>, like gpio3. Some GPIO drivers use more complex pin names like gpio33_pe11. Have a look at the USING GPIO section for information on how to set up the operating system. Normally, the pin will be active high but if the pin name is prefixed with an exclamation mark it will be active low instead. For some hardware platforms you may need to also set the GPIO_PATH configuration variable.

GPIO_PATH
    Use this configuration variable to set the path to the sys control devices for GPIO. This normally is /sys/class/gpio but on some hardware, like the Orange Pi, the path is /sys/class/gpio_sw.

PTT_GPIOD_CHIP
    The GPIO chip to use for PTT. The application tries to figure out whether the value is the path to the GPIO chip, its name, label or number. Example: PTT_GPIOD_CHIP=gpiochip0

PTT_GPIOD_LINE
    If GPIOD was specified in PTT_TYPE, set this config variable to the gpiod line of the GPIO pin to use. If a number is specified it is assumed to be the GPIO pin offset within the chip. If a pin name is specified SvxLink will try to find a pin with that name within the chip. Normally, the pin will be active high but if the pin specification is prefixed with an exclamation mark it will be active low instead. For some hardware platforms you may need to also set the PTT_GPIOD_CHIP configuration variable, if the pin you want to use is not on the default GPIO chip. Example: PTT_GPIOD_LINE=17

PTT_PTY
    If PTT_TYPE is set to "PTY" this configuration variable will set the path for the PTY slave softlink that is used by the external script to communicate to SvxLink. SvxLink sends a 'T' to start transmitting and a 'R' to turn the transmitter off. This can be used by an external script to interface custom devices, modems or other hardware to SvxLink. Look for nhrcx.pl to see an example. It is possible to specify the same PTY for multiple functions (e.g. squelch, DTMF etc) in both TX and RX configurations. This may be good if there is one script handling all functions.

HID_DEVICE
    Define the device node where your hidraw device is accessible at. Example: HID_DEVICE=/dev/hidraw3

HID_PTT_PIN
    Define the pin your ptt control is connected to. Valid parameters are are GPIO1,GPIO2,GPIO3,GPIO4. Note that some sound cards like SSS1621 may not support GPIO3 and GPIO4! You can invert the behavior with a "!" in front of the name. Only one value is supported.

SERIAL_SET_PINS
    Set the specified serial port pins to a static state. This can be good if using a pin for reference voltage or if a pin have to be in a certain state to not interfere with the operation of some equipment. There are two pins that are possible to use, RTS and DTR. If prefixed with an exclamation mark (!), the pin will be cleared and if not it will be set. This configuration variable can only be used when PTT_TYPE is set to "SerialPin". Example: SERIAL_SET_PINS=RTS!DTR will set RTS and clear DTR.

PTT_HANGTIME
    Use this configuration variable to set a PTT hangtime. This can be good to have on a transmitter in combination with using a tone squelch. When the transmitter is ordered to stop transmitting, the tone is immediately turned off, causing the squelch to close on the other side. Since the transmitter keeps transmitting for a while, no squelch tail will be heard. Another use is on a remote receiver link transmitter where you don't want the transmitter to turn on and off between transmissions or if the squelch close and open quickly due to for example mobile flutter.

TIMEOUT
    This is a feature that will prevent the transmitter from getting stuck transmitting. Specify the number of seconds before the transmitter is turned off. Note that this is a low level security mechanism that is meant to only kick in if there is a software bug in SvxLink. Just so that the transmitter will not transmit indefinitely. It is not meant to be used to keep people from talking too long.

TX_DELAY
    The number of milliseconds (0-1000) to wait after the transmitter has been turned on until audio is starting to be transmitted. This can be used to compensate for slow TX reaction or remote stations with slow reacting squelches.

CTCSS_FQ
    The frequency in Hz of the CTCSS tone to transmit. It is possible to specify fractions using "." as decimal comma (e.g. 136.5). For the tone to be transmitted the CTCSS_LEVEL variable must also be setup and also the TX_CTCSS variable in the logic core configuration section.

CTCSS_LEVEL
    The level in dBFS of the CTCSS tone to transmit. A value of 0 is the highest level and lower (negative) values give a lower level. What level to set depend on multiple factors like the audio calibration settings and the low-pass characteristics of the hardware. Assuming an ideal audio path with a completely flat frequency response over the whole audio spectrum, including the CTCSS frequency band, and a standard audio calibration where maximum FM deviation corresponds to -6 dBFS, the following applies. The FM deviation of the CTCSS tone should be in between 500-800 Hz if using an FM channel with a maximum deviation of 5 kHz. Given that you can calculate what the level in dBFS should be:
      Llow = 20 * log10(500/5000) - 6 = -26
      Lmid = 20 * log10(650/5000) - 6 = -24
      Lhigh = 20 * log10(800/5000) - 6 = -22 The default in the configuration file is -24. For the tone to be transmitted the CTCSS_FQ variable must also be set up and also the TX_CTCSS variable in the logic core configuration section.

PREEMPHASIS
    Enable this feature if you are modulating the FM modulator directly, like through a 9k6 packet radio input. If no preemphasis filter is applied to the audio, it will sound very dark when received. If you modulate the transmitter through the microphone input the radio will apply a preemphasis filter so this feature should be disabled. 0=disabled, 1=enabled.

DTMF_TONE_LENGTH
    The duration, in milliseconds, of DTMF digits transmitted on this transmitter. 100ms is the default.

DTMF_TONE_SPACING
    The spacing, in milliseconds, between DTMF digits transmitted on this transmitter. 50ms is the default.

DTMF_DIGIT_PWR
    The power, in dB, of DTMF digits transmitted on this transmitter. Zero dB will give the same power in the generated signal as there is in a maximum amplitude (full scale) sine wave. -15dB is the default.

TONE_SIGLEV_MAP
    It is possible to transmit one of ten tones along with the normal transmission to indicate a signal strength value to the receiver. This is of most use when using a local transmitter as a link transmitter in a RemoteTrx. It is not implemented, and probably not useful, in SvxLink Server. Another requirement is that SvxLink has been compiled in 16kHz mode. Otherwise this feature is disabled. The TONE_SIGLEV_MAP configuration variable is used to map tones to signal level values. It is a comma separated list of exactly ten values in the 0 - 100 range. The first value map to the 5500Hz tone, the second to the 5600Hz tone and so on. The last value map to the 6400Hz tone. What levels the tones should be mapped to depends on the tone receiver implementation. Typically, if using a SvxLink application as a receiver, the TONE_SIGLEV_MAP should be the same in the RX configuration for that node.

TONE_SIGLEV_LEVEL
    It is possible to transmit one of ten tones along with the normal transmission to indicate a signal strength value to the receiver. This is of most use when using a local transmitter as a link transmitter in a RemoteTrx. It is not implemented, and probably not useful, in SvxLink Server. Another requirement is that SvxLink has been compiled in 16kHz mode. Otherwise this feature is disabled. The TONE_SIGLEV_LEVEL configuration variable is used to set the tone level. It is a value in the 1-100 range which indicate the output level in percent of the maximum possible level. The default is 10.

LADSPA_PLUGINS
    Used to set up one or more LADSPA plugins to process the transmitted audio. The processing chain is applied right at the top of the transmitter audio processing and will only affect how the audio sounds. Any digital signal processing done on the audio after that, like DTMF, CTCSS etc, is unaffected. See "LADSPA PLUGIN USAGE" for more information.

MASTER_GAIN
    This configuration variable can be used to fine tune or increase the audio gain for all transmitted sound if it's not possible to do using the normal sound card hardware gain controls. The gain should be given in dB and can be both positive and negative.

OB_AFSK_ENABLE
    Set to 1 to enable transmission of metadata like signal level measurements, DTMF digits and tone detections via out-of-band (OB) AFSK. The out-of-band AFSK is transmitted above the voice band so that it is possible to transmit AFSK bursts at the same time as someone is speaking. The AFSK bursts are filtered out before the audio is handed on to the next stage so normal users should never hear the AFSK bursts. The AFSK feature is typically used on a remote receiver uplink. The protocol used is SvxLink specific. Data is transmitted in 300Bd with a shift of 170Hz and a center frequency of 5500Hz. The RemoteTrx application have the capability to transmit this protocol.

OB_AFSK_VOICE_GAIN
    To be able to send both voice and AFSK at the same time it may be necessary to lower the level of the voice audio as to not overdrive the transmitter. This is compensated in the link receiver by amplifying the voice audio back to its original level. This configuration variable should thus be set to the negated value of the same configuration variable in the receiver section of the receiving node. If it's set to 6dB in the receiver configuration it should be set to -6dB here.

OB_AFSK_LEVEL
    The out-of-band AFSK modulation level in dBFS (dB full scale). Default is -6dB.

OB_AFSK_TX_DELAY
    The number of milliseconds to send AFSK flag bytes before sending the actual data when transmitting an out-of-band packet.

IB_AFSK_ENABLE
    Set to 1 to enable transmission of an initial signal level measurement via in-band (IB) AFSK. This is used in cooperation with the out-of-band AFSK feature to quickly transfer a signal level measurement to get the squelch opened. The in-band AFSK is transmitted in the voice band and can thus use the higher baudrate of 1200Bd. Since it's only transmitted when the squelch is closed the end user will not hear the AFSK burst. The AFSK feature is typically used on a remote receiver uplink. The protocol used is SvxLink specific. Data is transmitted in 1200Bd with a shift of 1000Hz and a center frequency of 1700Hz. The RemoteTrx application have the capability to transmit this protocol.

IB_AFSK_LEVEL
    The in-band AFSK modulation level in dBFS (dB full scale). Default is -6dB.

IB_AFSK_TX_DELAY
    The number of milliseconds to send AFSK flag bytes before sending the actual data when transmitting an in-band packet.

CTRL_PTY
    Set this configuration variable to the path of a PTY to use for controlling a transmitters frequency and modulation. This can be used to interface a transmitter to SvxLink using a translation script, like trx_pty_ctrl.py. To set the transmit frequency, SvxLink will send the sequence "F<frequency>;". The frequency will be in Hz, e.g. F145550000; will be sent to set the receiver to 145.550MHz. To set the modulation the command is "M<modulation>;". Look at the documentation of the MODULATION configuration variable to see which modulations are available. To set "normal" 25kHz channel spaced FM the command would be MFM;. It is possible to specify the same PTY for multiple functions (e.g. squelch, ptt etc) in both TX and RX configurations. This may be good if there is one script handling all functions.

  Networked Transmitter Section
A networked transmitter section is used to specify the configuration for a transmitter connected through a TCP/IP network. In the default configuration file there is a networked transceiver configuration section called NetTx. The section name could be anything. It should match the TX configuration variable in the logic core where the transmitter is to be used. The available configuration variables are described below. How to use a networked transmitter is further described in the remotetrx(1) manual page.

TYPE
    Always "Net" for a networked transmitter.

TX_ID
    A single character ident for this transmitter. It is for example used in state events published by transmitters through a STATE_PTY or other state event consumers within SvxLink. SvxLink cannot at this moment get the TX ident from the remote transmitter so it must be specified here.

HOST
    The hostname or IP address of the remote transmitter host.

TCP_PORT
    The TCP port that RemoteTrx listen on. The default is 5210.

LOG_DISCONNECTS_ONCE
    Set this configuration variable to 1 to suppress logging of multiple disconnect messages in a row, like when there is no RemoteTrx running on the other side. Thus, failed reconnect attempts will not be logged at all. This may be of use if a RemoteTrx is missing for a long time or if it's only used from time to time. The default is 0 which means that all reconnect attempts will be logged.

AUTH_KEY
    This is the authentication key (password) to use to connect to the RemoteTrx server. The same key have to be specified in the RemoteTrx configuration. If no key is specified in the RemoteTrx config, the login will be unauthenticated. A good authentication key should be 20 characters long. If the same RemoteTrx is used for both RX and TX, the same key must be specified in the RX as well as in the TX configuration section. The key will never be transmitted over the network. A HMAC-SHA1 challenge-response procedure will be used for authentication.

CODEC
    The audio codec to use when transferring audio to this remote transmitter. Available codecs are: RAW (512kbps), S16 (256kbps), GSM (13.2kbps), SPEEX (8-25kbps), OPUS (8-64kbps). These are raw bit-rate values. There will be some overhead added to this so the real bit-rates on the wire are a little bit higher. The OPUS codec is the most modern one and it also have the best quality for a given bit-rate. There also is a NULL codec that will just throw away samples which can be used in special situations when the audio is sent through another audio path.

SPEEX_ENC_FRAMES_PER_PACKET
    Speex encoder setting. Each Speex frame contains 20ms audio. If using a low bit-rate configuration, the network overhead will be quite noticeable if sending each frame in its own packet. One way to lower the overhead is to send multiple frames in each network packet. The drawback with doing this is that you get more delay. If setting this option to something like 4 (default), the delay will be about 4x20=80ms.

SPEEX_ENC_QUALITY
    Speex encoder setting. Specify the encoder quality using a number between 0-10. Lower values give poorer quality and lower bit-rates.

SPEEX_ENC_BITRATE
    Speex encoder setting. Specify the bit-rate to use. Speex will snap to the nearest lower possible bit-rate. Possible values range from 2150 to 24600 bps. You should probably not specify quality at the same time as bit-rate. Not sure though...

SPEEX_ENC_COMPLEXITY
    Speex encoder setting. The complexity setting (0-10) tells the encoder how much CPU time it should spend on doing a good job. The difference in SNR between the lowest and highest value is about 2dB. Set it as high as possible without overloading the CPU on the encoding computer (check CPU usage using command "top").

SPEEX_ENC_VBR
    Speex encoder setting. Enable (1) or disable (0) variable bit-rate encoding. If enabled, the encoder will try to keep a constant quality by increasing the bit-rate when needed.

SPEEX_ENC_VBR_QUALITY
    Speex encoder setting. The quality (0-10) to use in variable bit-rate mode.

SPEEX_ENC_ABR
    Speex encoder setting. The average bit-rate encoding will try to keep a target bit-rate by continuously adjusting the quality. This configuration variable specify the target bit-rate and enable ABR. It also need to have VBR enabled so don't force it to off.

SPEEX_DEC_ENHANCER
    Speex decoder setting. Enable (1) or disable (0) the perceptual enhancer in the decoder. Perceptual enhancement is a part of the decoder which, when turned on, attempts to reduce the perception of the noise/distortion produced by the encoding/decoding process. In most cases, perceptual enhancement brings the sound further from the original objectively (e.g. considering only SNR), but in the end it still sounds better (subjective improvement).

OPUS_ENC_FRAME_SIZE
    Opus encoder setting. Specify how large, in milliseconds, each audio packet should be. Default: 20ms.

OPUS_ENC_COMPLEXITY
    Opus encoder setting. The complexity setting (0-10) tells the encoder how much CPU time it should spend on doing a good job. Set it as high as possible without overloading the CPU on the encoding computer (check CPU usage using command "top"). Default: 10.

OPUS_ENC_BITRATE
    Opus encoder setting. This is the bit-rate that the encoder will encode for. Rates from about 8000 to 64000 bits per second are meaningful but the codec can handle from like 2500 to 512000 bps. Default: 20000bps.

OPUS_ENC_VBR
    Opus encoder setting. Enable (1) or disable (0) variable bit-rate encoding. If enabled, the encoder will try to keep a constant quality by increasing the bit-rate when needed and decrease it when the quality can be assured with a lower bit-rate. The target average bit-rate is the one set by OPUS_ENC_BITRATE. Default: 1.

  Multi Transmitter Section
A multi transmitter section is used if one wants to transmit on multiple transmitters simultaneously. The name of the section can be anything. Just point it out from another transmitter specification like the TX variable in a Logic core configuration.

TYPE
    Always "Multi" for a multi transmitter section.

TRANSMITTERS
    A comma separated list of transmitters.

  Module Section
A module section contain the configuration for a specific module. It have some general configuration variables and some module specific configuration variables. The general configuration variables are listed below.

NAME
    The name of the module. This name must match the namespace used in the TCL event handling script. If not set, NAME will be set to the section name.

PLUGIN_NAME
    The base name of the plugin. For example if this configuration variable is set to Foo, the core will look for a plugin called ModuleFoo.so. If not set, PLUGIN_NAME will be set to the same value as NAME.

ID  Specify the module identification number. This is the number used to access the module from the radio interface.

TIMEOUT
    Specify the timeout time, in seconds, after which a module will be automatically deactivated if there has been no activity. Not including this parameter removes the timeout.

MUTE_LOGIC_LINKING
    Set to 1 to mute all logic linking audio when the module is activated or 0 to keep logic linking unmuted at all times. Default is 1 (mute).

Module specific configuration variables are described in the man page for that module. The documentation for the Parrot module can for example be found in the ModuleParrot.conf(5) manual page.

  LocationInfo
The LocationInfo configuration section is used to specify information that should be sent into the APRS network and also to the Echolink link status page. The use of location info is activated by setting the LOCATION_INFO configuration variable in the GLOBAL section. The following configuration variables can be used in the LocationInfo configuration section.

STATUS_SERVER_LIST
    Enter a space separated list of EchoLink status servers that should be used to send node status beacons. Your node information can be found on https://www.echolink.org/links.jsp. The format is host:port. Host - hostname or IP address, port - UDP port. Don't change the default unless you know what you are doing. If you don't want to update the EchoLink status server, comment out this configuration variable. Example:
    STATUS_SERVER_LIST=aprs.echolink.org:5199

APRS_SERVER_LIST
    This configuration variable specifies connection parameters for connecting to an APRS server network using the TCP protocol. In this case, the positioning information is forwarded to the worldwide APRS network. Have a look at https://aprs.fi/. To choose a suitable APRS server from the so called tier 2 network, have a look at https://www.aprs2.net/. Either choose a specific server or one of the regional addresses. The regional addresses bundle all APRS servers within a region so that a random tier 2 server is chosen within the region. There are five regions defined: noam.aprs2.net - North America, euro.aprs2.net - Europe, asia.aprs2.net - Asia, soam.aprs2.net - South America and Africa, aunz.aprs2.net - Australia and New Zealand. The format is a space separated list of host:port entries. Host - hostname or IP address, port - TCP port. Example:
    APRS_SERVER_LIST=euro.aprs2.net:14580

FILTER
    Set the APRS-IS filter expression to use. The filter is used to decide which APRS packets the APRS-IS server should forward to SvxLink. Documentation on filter expressions can be found here: https://www.aprs-is.net/javAPRSFilter.aspx Example:
    FILTER=m/10

LON_POSITION
    The longitude of the station position, entered as "degrees.arcminutes.arcseconds" Example:
    LON_POSITION=09.02.20E

LAT_POSITION
    The latitude of the station position, entered as "degrees.arcminutes.arcseconds" Example:
    LAT_POSITION=51.02.22N

CALLSIGN
    Enter your callsign for the APRS network. If one of the Echolink prefixes are specified an Echolink object and Echolink status will be published. The Echolink prefix indicate the type of station and can be either "ER-" for repeaters or "EL-" for links. Examples:
    CALLSIGN=EL-DL1ABC # callsign for a link
    CALLSIGN=DB0ABC-1 # callsign (with SSID 1) for node without Echolink

SOURCE_CALLSIGN
    Specify the callsign to use as the APRS source address. That callsign must comply with the AX.25 source callsign specification. If this configuration variable is not specified, the callsign will be extracted from the CALLSIGN config variable. Any EL- or ER- prefix will be stripped off. Example:
    SOURCE_CALLSIGN=DB0ABC-1

LOGIN_CALLSIGN
    Specify the callsign to use to log in to the APRS-IS network. The login callsign must comply with the APRS-IS specification found at https://www.aprs-is.net/connecting.aspx. If this configuration variable is not specified, the callsign will be the same as the source callsign. Example:
    LOGIN_CALLSIGN=DB0ABC-2M

FREQUENCY
    The tx-frequency of the link/repeater in MHz. For repeaters, the TX_OFFSET configuration variable should be used to specify the repeater shift. Example:
    FREQUENCY=430.050 # tx-frequency is 430.050 MHz

FREQUENCY_SEPARATOR
    Use the specified character to separate the PHG from the frequency. Unfortunately different tranceivers understand different APRS formats. For example the Yaesu FTM-510D require that no separator is used and the Kenwood TM-D710 require a separator (e.g. "/") to be present. The default is to use a slash as the separator charachter.

TX_OFFSET
    The tx offset is the number of kHz from the FREQUENCY where the node is listening for other stations. For a repeater that is the "shift" (e.g. -600). For a simplex node it's most often 0. The limits for the offset is [-9990,+9990] kHz. If not specified it will be set to 0. Note that when the APRS packet is transmitted the value is expressed in tens of kHz. So if the configuration parameter is set to -600 kHz, it will be sent as -060.

TX_POWER
    The power of your transmitter in watts. The maximum power allowed in the APRS protocol is 81 watts so if a power grater than that is specified it will be set to that maximum value. However, the advice is to set it to the actual power if the protocol evolves to handle higher powers in the future. So if your transmitter outputs 200 watts, set it to that. Example:
    TX_POWER=10 # tx output is 10 watts

NARROW
    Setting this configuration variable to 1 will indicate that this node is using narow band FM, 12.5 kHz channel spacing. The default is 0, meaning a channel spacing of 25kHz.

ANTENNA_GAIN
    The gain of your antenna in dBd. Example:
    ANTENNA_GAIN=5 # antenna gain is 5 dBd

ANTENNA_HEIGHT
    The height of the link-/repeater antenna in meters or feet above the terrain (HAAT), NOT sealevel. Example:
    ANTENNA_HEIGHT=10m # 10 meters above the ground
    ANTENNA_HEIGHT=90 # 90 feet

ANTENNA_DIR
    Main beam direction of the antenna in degrees. If an omni direction antenna is used, specify -1 as the direction. Example:
    ANTENNA_DIR=-1 # an omni directional antenna is used
    ANTENNA_DIR=128 # main beam direction is 128 degrees

PATH
    When connecting to APRS-IS, this configuration variable is best left commented out so that the default is used (TCPIP*). Only the qAR and qAO constructs may be added to the path. Do not change it unless you really know what you are doing. If you don't connect to APRS-IS you may be able to use this config variable to control the way the forwarding of your packets inside the RF APRS network is done. In some cases it has to be changed according to local requirements. Please contact your local APRS sysop for further information. Changes should be made only according to the NEWn-N paradigm. Set it to WIDE1-1 if you are unsure of its setting. But once again, leave it unset if you are not sure that it need to be set. Examples:
    PATH=WIDE1-1
    PATH=WIDE1-1,WIDE2-2

BEACON_INTERVAL
    The interval, in minutes, with which beacons will be sent to the APRS network. A good value is 10 minutes. If your beacon is gated via RF in a crowded area, it may be necessary to increase the interval a bit to keep the APRS traffic on RF produced by the APRS RF gate as low as possible. Intervals shorter than 10 minutes will be changed to 10. Example:
    BEACON_INTERVAL=20 # APRS-beacons will be sent every 20 minutes.

SYMBOL
    Specify which APRS symbol that should be displayed on maps. Symbols are specified using two characters where the first one determines which symbol table to use and the second one select the actual symbol to use from the selected table. So for example "/-" is a house and "/r" mean a repeater tower. For all details abount APRS symbols, have a look at the latest documentation: https://www.aprs.org/symbols/symbolsX.txt. The specified symbol is only applied to the base callsign and not to the Echolink one. Example:
    SYMBOL=/r

TONE
    The CTCSS sub-audible tone that is to be used for operation over your link or repeater. If you don't use tone control set it to 0. Examples:
    TONE=136.5 # we are using a CTCSS-tone of 136.5 Hz
    TONE=0 # we don't use CTCSS sub-audible or call tones
    TONE=1750 # the link/repeater use a tone burst of 1750 Hz

STATISTICS_INTERVAL
    Defines the interval in minutes in that an APRS statistics (telemetry) are sent into the aprs network. Range: 5-60 minutes, default is 10 minutes

STATISTICS_LOGIC
    The name of the logic core that statistics (telemetry) should be sent for. If this configuration varible is not set, telemetry will be sent for all logics. That will probably lead to unpredictable results but it depend on what logic core types that are loaded in SvxLink. Example: STATISTICS_LOGIC=SimplexLogic

COMMENT
    Specify a short comment here, maybe a link to your website or information that could be interesting for others. The length must not exceed 36 characters and may not have control characters like "Carriage Return" (\r) or "Line Feed" (\n) inside. Make your comment as short as you can to give users with a small display (TH-D7) the chance to display the full comment text. Example:
    COMMENT=SvxLink by SM0SVX

PTY_PATH
    Specify a path to a communications PTY that can be used by external applications to inject APRS packets into the APRS-IS network. A source callsign specified with XXXXXX (6 X:es) will be replaced with the configured source callsign. Example:
        PTY_PATH=/dev/shm/locationinfo
        $ echo 'XXXXXX>APSVX1,TCPIP*:>Testing SvxLink APRS' > /dev/shm/locationinfo

DEBUG
    Set to 1 to print which APRS packets that are sent into or received from the APRS network.

AUDIO DEVICE SPECIFICATIONS
The AUDIO_DEV configuration variables specify which audio device to use for a receiver or transmitter. SvxLink support a number of different audio input and output devices. The format of the configuration variable is "type:dev_spec". There are three different types of audio devices supported, "alsa", "oss" and "udp". The "alsa" type will use the specified Alsa device. Example: "alsa:plughw:0". Describing the format of Alsa device names is outside the scope for this document. The "oss" type will use the specified OSS audio device. Example "oss:/dev/dsp". OSS is the old sound system used by Linux. Alsa should be used when possible. The "udp" type is not really an audio device but instead will read and write audio from/to a UDP socket. This can be used to interface SvxLink to all sorts of audio sources/sinks capable of streaming raw audio through UDP. One example usage is to interface SvxLink with GNU Radio. Example: "udp:127.0.0.1:10000". Note however that the only supported format is raw 16 bit signed samples, two interleved channels. Sampling frequency can be chosen using the CARD_SAMPLE_RATE config variable as usual.

USING GPIO
GPIO (General Purpose IO) is used to access hardware pins that are made available for example on an embedded system. Before starting to use a pin in SvxLink some setup need to be done in the operating system. With the standard distribution of SvxLink there is a pair of scripts that help with setting up and taking down the GPIO pins. The scripts are named svxlink_gpio_up and svxlink_gpio_down. The configuration file, which can be found among the other SvxLink configuration files (typically in /etc/svxlink), is called gpio.conf.

CALIBRATING THE SIGNAL LEVEL DETECTOR
The signal level detector is used when using multiple receivers or when using the SIGLEV squelch. The signal level is used by a voter to choose the receiver with the highest signal strength. The choice is made directly after squelch open. For the voter to make a correct choice, the signal level detector must be calibrated on each receiver. To use the noise signal level detector, first set SIGLEV_DET=NOISE or, since NOISE is the default, just make sure that it's unset. There are two configuration variables that is used to calibrate the detector. They are SIGLEV_SLOPE and SIGLEV_OFFSET in a local receiver section. The slope is the gain of the detector and the offset is used to adjust the detector so that when there is no input signal, the detector will return 0. The goal is to adjust the detector so that when no signal is received, a value of 0 is produced and when full signal strength is received, a value of 100 is produced. It will never be exact but that does not matter as long as each receiver produce a measurement that roughly has the same siglev value as the other receivers for a certain signal level. The calibration is normally done by using the siglevdetcal(1) application. To be able to do a correct calibration, it must be possible to open the squelch so that only noise is received. The antenna cable should be disconnected or a dummy load should be used. WARNING: Before starting the siglevdetcal application, pull the PTT cable since the PTT might get triggered during the calibration procedure. The siglevdetcal utility will also measure the CTCSS tone SNR offset so that the CTCSS_SNR_OFFSETS configuration variable can be set up to a proper value. If the siglevdetcal application cannot be used for some reason, the manual procedure below might be used. This procedure will only work for a receiver with unsquelched audio. Note: To calibrate a remote receiver it must be connected to the SvxLink server. Otherwise the squelch will not open.

    1   Connect a dummy load or disconnect the antenna from the transceiver. If you disconnect the antenna, make sure to also disconnect the PTT.

    2   Set SIGLEV_SLOPE=1 and SIGLEV_OFFSET=0 and restart SvxLink.

    3   Open the squelch so that there is only noise coming into SvxLink.

    4   Use a second transceiver to make a short, unmodulated transmission. Release the PTT when the "Squelch OPEN" message is printed. Repeat this for about five times.

    5   Calculate the mean diff (open level - close level) and the mean lower (squelch close) value. Make sure to use at least four significant digits in your calculations.

    6   SIGLEV_SLOPE = 100 / (mean diff)

    7   SIGLEV_OFFSET = - (mean lower) * SIGLEV_SLOPE

    8   After changing SIGLEV_SLOPE and SIGLEV_OFFSET, restart SvxLink and check to see that the squelch open value is now around 100 and the squelch close value is around 0.

STATE PTY FORMAT
The format of the output from the state PTY is:

    <timestamp> <context>:<event name> <event data>
        where the different parts mean:

            timestamp = <seconds since 1 jan 1970>.<milliseconds>
                context = Name of context
                    event_name = Name of event
                        event data = Event specific data
                            An event must be all on one line so there must be no line breaks. JSON event data in the examples below use line breaks to be easier to read.

                            Pretty printing events containing JSON formatted event data can be done using the following one-liner.

                                awk '{ print "{

                                    The following specific events exist.

                                    Tx:state
                                        Report the state for a transmitter. The event specific data is a JSON object. Example:

                                          {
                                            "id": "T",
                                            "name": "Tx1",
                                            "transmit": false
                                          }
                                            where the different fields mean:

                                                name = Configuration file section name for transmitter
                                                    id = The transmitter ID from configuration
                                                        transmit = Set to true if the transmitter is transmitting

                                                            Voter:sql_state
                                                                Report the state of all squelches and signal levels for all receivers. The event specific data is a JSON array containing an object for each receiver. Example:

                                                                  [
                                                                    {
                                                                      "name": "Rx1",
                                                                      "id": "E",
                                                                      "enabled": true,
                                                                      "sql_open": true,
                                                                      "active": true,
                                                                      "siglev": 59
                                                                    },
                                                                    {
                                                                      "name": "Rx2",
                                                                      "id": "R",
                                                                      "enabled": true,
                                                                      "sql_open": true,
                                                                      "active": false,
                                                                      "siglev": 33
                                                                    },
                                                                    {
                                                                      "name": "Rx3",
                                                                      "id": "D",
                                                                      "enabled": false
                                                                    }
                                                                  ]
                                                                    where the different fields mean:

                                                                        name = Configuration file section name for receiver
                                                                            id = The receiver ID from configuration
                                                                                enabled = Set to true if the receiver is enabled
                                                                                    sql_open = Set to true if the squelch is open
                                                                                        active = Set to true if the receiver is the active one, selected by the voter
                                                                                            siglev = The measured signal level

LADSPA PLUGIN USAGE
LADSPA is a framework for sharing pluggable audio components and there are numerous plugins to choose from. Each plugin has a name ("label") and zero or more configuration parameters ("control input ports"). To find out which plugins are installed on your system, use the "listplugins" command. If you are missing some plugin it may be available to install using your package manager (rpm/yum/dnf, deb/apt etc). To find out more information about a plugin, use the "analyseplugin" command (e.g. analyseplugin filter hpf). Learn more about the LADSPA framework in their official documentation. In SvxLink only plugins that have exactly one audio input and one audio output can be used, so all stereo plugins are excluded for example. The same thing is valid for input-only or output-only plugins. The analyseplugin utility will, among other things, list the ports. All ports that are typed as "input, control" can be used to configure the plugin. Valid range and a default value may also be listed. The format for the LADSPA_PLUGINS configuration variable in SvxLink is "label1:port1:port2:...:portN,label2:port1:port2:...:portN,@MyPlugConfig,...". Note that only control input ports are counted here so when applying the parameters any intermingled ports of other types are skipped. If an instance config start with an @-sign, a configuration section with the given name is used to configure the plugin. There must be a LABEL configuration item and the rest of the configuration variables in that section must match input control port names in the plugin instance specified by LABEL. The config variable names are matched against the beginning of the port names but does not have to match the whole name. Example:
  LADSPA_PLUGINS=hpf:1000,@Tx1_Compressor
  [Tx1_Compressor]
  LABEL=tap_dynamics_m
  Attack=4
  Release=500
  Offset Gain=15
  Makeup Gain=15
  Function=13

FILES

/etc/svxlink/svxlink.conf (or deprecated /etc/svxlink.conf)
    The system wide configuration file.

~/.svxlink/svxlink.conf
    Per user configuration file.

/etc/svxlink/svxlink.d/*
    Additional configuration files. Typically one configuration file per module.

AUTHOR
Tobias Blomberg (SM0SVX) <sm0svx at svxlink dot org>

REPORTING BUGS
Bugs should be reported using the issue tracker at https://github.com/sm0svx/svxlink. Questions about SvxLink should not be asked using the issue tracker. Instead use the group set up for this purpose at groups.io: https://groups.io/g/svxlink

SEE ALSO
svxlink(1), remotetrx(1), siglevdetcal(1), devcal(1)