svxlink.conf.5

.TH SVXLINK.CONF 5 "JULY 2014" Linux "File Formats"
.
.SH NAME
.
svxlink.conf \- Configuration file for the SvxLink server
.
.SH DESCRIPTION
.
.B svxlink
is a general purpose voice service system for ham radio use. This man-page
describe the SvxLink server configuration file format.
.P
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:
.BR $HOME/.svxlink/svxlink.conf .
If no user specific configuration file can be found, SvxLink will look for
the system wide configuration file
.BR /etc/svxlink/svxlink.conf .
The
.B --config
command line option may also be used to specify an arbitrary configuration file.
.
.SH 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".
.P
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).
.
.SH CONFIGURATION VARIABLES
.
Here is the description of all configuration variables that SvxLink understands. The
configuration variables are described section for section.
.
.SS GLOBAL
.
The GLOBAL section contains application global configuration data.
.TP
.B MODULE_PATH
Specify where the SvxLink modules can be found. The default is /usr/lib/svxlink 
.TP
.B LOGICS
Specify a comma separated list of logic cores that should be created. The logic core is
the thing that ties the transciever 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
behaviour of the logic core is specified.
.TP
.B 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 are
ignored.
.TP
.B TIMESTAMP_FORMAT
This variable specifies the format of the timestamp that is written in front of
each row in the log file. The format string is in the same format as specified
in the
.BR 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 timestamp representation. Other
examples of format specifiers are:
.RS
.IP \(bu 4
.BR %d " - The day of the month as a decimal number (range 01 to 31)"
.IP \(bu 4
.BR %b " - The abbreviated month name according to the current locale"
.IP \(bu 4
.BR %Y " - The year as a decimal number including the century"
.IP \(bu 4
.BR %H " - The hour as a decimal number using a 24-hour clock (range 00 to 23)"
.IP \(bu 4
.BR %M " - The minute as a decimal number (range 00 to 59)"
.IP \(bu 4
.BR %S " - The second as a decimal number (range 00 to 61)"
.IP \(bu 4
.BR %f " - Fractional seconds in millisecond resolution (000-999)"
.P
The last one (%f) is a SvxLink specific formatting specifier.

Example: TIMESTAMP_FORMAT="%d %b %Y %H:%M:%S.%f" would give a timestamp looking
something like: "29 Nov 2005 22:31:59.875".
.RE
.TP
.B 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 som 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 cheeper, 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.
.TP
.B 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 independenly to drive two transceivers. When using the sound
card in mono mode, both left and right channels transmit/receive the same
audio.
.TP
.B LOCATION_INFO
Enter the section name that contains information required for transfering
positioning data to location servers. Setting this item makes the system
visible on the EchoLink link status page and the APRS network.
.TP
.B LINKS
Enter here a comma separated list of section names that contains the 
configuration information for linking logics together (see Logic Linking).
.
.SS 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. 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.
.TP
.B 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.
.TP
.B RX
Specify the configuration section name of the receiver to use. All configuration
for the receiver is done in the specified configuration section.
.TP
.B TX
Specify the configuration section name of the transmitter to use. All
configuration for the transmitter is done in the specified configuration
section.
.TP
.B MODULES
Specify a comma separated list of configuration sections for the modules to
load. This tells SvxLink which modules to actually load on startup.
.TP
.B CALLSIGN
Specify the callsign that should be announced on the radio interface.
.TP
.B 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.
.TP
.B 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.
.TP
.B 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.   
.TP
.B 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. This really only is of
use when using a radio that it is difficult to send DTMF digits from, like the Yaesu VX-2
handheld. The down side of enabling this option is that the DTMF detection some times
false trigger on voice. This can cause interresting situations when all of a sudden a
module get activated in the middle of a QSO.
.TP
.B 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 occurr.
The default location is /usr/share/svxlink/events.tcl.
.TP
.B 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.
.TP
.B 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. 
.TP
.B 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. 
.TP
.B 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:
.BR 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.
.RS
.IP \(bu 4
.BR 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.
.IP \(bu 4
.BR LOGIC
will transmit CTCSS tone when there is incoming traffic from another logic
core.
.IP \(bu 4
.BR MODULE
will transmit CTCSS tone when there is incoming traffic from a module.
.IP \(bu 4
.BR 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.
.IP \(bu 4
.BR ALWAYS
will always transmit a CTCSS tone as soon as the transmitter is turned on.
.RE
.TP
.B 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.
.TP
.B 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.
.TP
.B 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.
.TP
.B 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
.TP
.B 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.
.TP
.B 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".
.TP
.B 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 at doing a
.B "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
.
.SS 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
.BR 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.
.TP
.B TYPE
The type for a simplex logic core is always
.BR Simplex .
.TP
.B 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.
.TP
.B 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.
.
.SS 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
.BR 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.
.TP
.B TYPE
The type for a repeater logic core is always
.BR Repeater .
.TP
.B 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.
.TP
.B IDLE_TIMEOUT
The number of seconds the repeater should have been idle before turning the 
transmitter off.
.TP
.B 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.
.TP
.B OPEN_ON_CTCSS
Use this configuration variable if it should be possible to open the repeater with 
a CTCSS tone (PL). The syntax of the value is tone_fq:min_length. The tone 
frequency is specified in whole Hz and the minimum tone length is specified in 
milliseconds. For examples if a 136.5 Hz tone must be asserted for two seconds for 
the repeater to open, the value 136:2000 should be specified.
.TP
.B 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.
.TP
.B 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.
.TP
.B 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.
.TP
.B 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.
.TP
.B 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.
.TP
.B 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.
.TP
.B 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.
.TP
.B 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.
.TP
.B 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.
.TP
.B 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.
.TP
.B IDENT_NAG_TIMEOUT
Tell repeater users that are not identifying to identify themselvs.
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.
.TP
.B 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.
.
.SS 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.
.TP
.B 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.
.TP
.B 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).
.TP
.B 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)
.TP
.B 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 splitted between files. Default: 0 (no limit)
.TP
.B 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)
.TP
.B 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)
.TP
.B 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)
.TP
.B 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)
.TP
.B 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:
.RS
.IP \(bu 4
.BR %f " - The full filename with full path"
.IP \(bu 4
.BR %d " - The directory part (what REC_DIR is set to)"
.IP \(bu 4
.BR %b " - The basename, that is, the filename without path and extension"
.IP \(bu 4
.BR %n " - The filename without path but with extension"
.P
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\\"
.BR
 ENCODER_CMD=/usr/bin/lame --quiet \\"%f\\" \\"%d/%b.mp3\\" && rm \\"%f\\"
.BR
 ENCODER_CMD=/usr/bin/speexenc \\"%f\\" \\"%d/%b.spx\\" 2>/dev/null && rm \\"%f\\"
.BR
 ENCODER_CMD=/usr/bin/opusenc \\"%f\\" \\"%d/%b.opus\\" 2>/dev/null && rm \\"%f\\"
.
.SS 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.
.P
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.
.
.SS 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).
.P
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
.TP
.B 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".
.TP
.B 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.
.TP
.B 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.
.TP
.B AUTOACTIVATE_ON_SQL
Enter a comma separated list of logics, which should automatically activate
the link if there is activity (e.g. squelch open) 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: AUTOACTIVATE_ON_SQL=MicSpkrLogic
.
.SS 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
.BR 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.
.TP
.B TYPE
Always "Local" for a local receiver.
.TP
.B AUDIO_DEV
Specify the audio device to use. Normally alsa:plughw:0. Have a look at the
AUDIO DEVICE SPECIFICATIONS chapter for more information.
.TP
.B 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.
.TP
.B SQL_DET
Specify the type of squelch detector to use. Possible values are: VOX, CTCSS,
SERIAL, EVDEV, SIGLEV, PTY, GPIO or HIDRAW.

The VOX squelch detector determines if there is a signal
present by calculating a mean value of the sound samples. The VOX squelch
detector behaviour 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_OFFSET, CTCSS_BPF_LOW, CTCSS_BPF_HIGH.

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.

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 SIGLEV_OPEN_THRESH and 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 easy protocol over a pseudo-tty device, 
created by SvxLink on runtime. 
An 'O' over this pty device indicate an open squelch, a 'Z' is a closed squelch.
Define the slave pty in 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 to see an example.

The HIDRAW squelch supports human interface devices (HID), USB devices
like CM108 soundcard e.g. used in the URI Echolink adapter made by DMK.
.TP
.B 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. 
.TP
.B 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.
.TP
.B 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. 
.TP
.B 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.
.TP
.B 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.
.TP
.B SQL_TIMEOUT
Use this configuration variable to set an upper limiti, 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, everthing is back
to normal. When it opens the next time a squelch open will be signalled.
For example, use this feature to make sure that a faulty receiver cannot block
the system indefinitly.
.TP
.B 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. 
.TP
.B VOX_THRESH
The threshold that the mean value of the samples must exceed for the squlech 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. 
.TP
.B CTCSS_MODE
This configuration variable set the CTCSS detection method used. These are the
ones to choose from:
.RS
.IP \(bu 4
.BR "0 (Default)"
Will choose the detection mode that is the default in the software. At the
moment this is the "Estimated SNR" mode.
.IP \(bu 4
.BR "1 (Neighbour 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.
.IP \(bu 4
.BR "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.
.IP \(bu 4
.BR "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.
.RE
.TP
.B 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.
.TP
.B 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 or 3 it
is helpful to set up the CTCSS_SNR_OFFSET config variable. This will make the
SNR estimation pretty good. Default threshold is 15dB.
.TP
.B 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 or 3 it
is helpful to set up the CTCSS_SNR_OFFSET config variable. This will make the
SNR estimation pretty good. Default threshold is 9dB.
.TP
.B CTCSS_SNR_OFFSET
This config variable is used when CTCSS_MODE is set to 0, 2 or 3. It will
adjust the estimated SNR value so that it becomes 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.
.TP
.B CTCSS_BPF_LOW
When CTCSS_MODE is set to 0, 2 or 3, 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.
.TP
.B CTCSS_BPF_HIGH
When CTCSS_MODE is set to 0, 2 or 3, 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.
.TP
.B 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 
.TP
.B 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
.TP
.B 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.
.TP
.B 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.
.TP
.B 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.
.TP
.B 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.
.TP
.B 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
.TP
.B SIGLEV_DET
Choose which type of signal level detector to use. There are two choices,
"NOISE" or "TONE". The  signal level detector is only needed when using
multiple receivers in a voter configuration or when using the SIGLEV squelch
type.

Type NOISE use a bandpass filter in the range of 5 - 5.5kHz
(CARD_SAMPLE_RATE >= 16000) or a highpass 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 spektrum (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.
.TP
.B 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
.TP
.B 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
.TP
.B SIGLEV_SLOPE
The slope (or gain) of the signal level detector. See chapter CALIBRATING THE
SIGNAL LEVEL DETECTOR below for more information.
.TP
.B SIGLEV_OFFSET
The offset of the signal level detector. See chapter CALIBRATING THE SIGNAL
LEVEL DETECTOR below for more information.
.TP
.B 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.
.TP
.B 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.
.TP
.B 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.
.TP
.B 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.
.TP
.B 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.
.TP
.B 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.
.TP
.B 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.
.TP
.B PEAK_METER
This is a help to adjust the incoming audio level. If enabled it will output a
message when distorsion 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.
.TP
.B DTMF_DEC_TYPE
Specify the DTMF decoder type. Set it to
.B INTERNAL
to use the internal software
DTMF decoder. To use the S54S interface featuring a hardware DTMF decoder, set
it to
.B S54S.
To control it over a pseudo tty device set it to
.B 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.
.B NONE
or commenting it out will disable DTMF detection.
.TP
.B DTMF_MUTING
Mute the audio during the time when a DTMF digit is being received. Note that
the audio will be delayed 75ms to give the DTMF 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 DTMF_MUTING are 0=disabled, 1=enabled.
.TP
.B 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.
.TP
.B DTMF_SERIAL
When using an external hardware DTMF decoder this config variable is used to
specify a serial port (e.g. /dev/ttyS0).
.TP
.B 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 symlink a very easy communication protocol is used to
tell SvxLink 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 to see an
example.

Example: /tmp/rx1_dtmf.
.TP
.B 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.
.TP
.B 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.
.TP
.B 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.
.RS
.IP \(bu 4
.BR pwr " - The power in the audio signal. Must be over about -50dB."
.IP \(bu 4
.BR 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.
.IP \(bu 4
.BR 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.
.IP \(bu 4
.BR rowq " - Quality of the row (low group) tone. Should be close to one."
.IP \(bu 4
.BR colq " - Quality of the column (high group) tone. Should be close to one."
.IP \(bu 4
.BR digit " - The digit mapped to the two detected tones."
.IP \(bu 4
.BR row3rd " - The row tone relation to its third overtone."
Should be close to zero. If it's not, the signal is probably distorted.
.IP \(bu 4
.BR col3rd " - The column tone relation to its third overtone."
Should be close to zero. If it's not, the signal is probably distorted.
.IP \(bu 4
.BR 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.
.RE
.TP
.B 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.
.TP
.B 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.
.TP
.B 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.
.TP
.B 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
.
.SS 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 wideband receiver. These USB
dongles can be bought cheeply 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 wideband 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 wideband 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 wideband 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.
.TP
.B FQ
The narrowband channel frequency to tune to.
.TP
.B WBRX
The configuration section for the wideband receiver to connect this DDR to.
See "Wideband Receiver Section" below.
.TP
.B 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.
.
.SS Wideband Receiver Section
.
A wideband receiver section is used to configure access to a wideband receiver
which can be used by a Digital Drop Receiver (DDR), described above, to handle
multiple narrowband 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:
.TP
.B TYPE
The type of wideband receiver used. The only supported values right now are
"RtlTcp" and "RtlUsb".
.TP
.B 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)
.TP
.B HOST
The name of the host that the rtl_tcp utility is running on (Default:
localhost).
.TP
.B PORT
The TCP port that rtl_tcp is listening on (Default: 1234).
.TP
.B SAMPLE_RATE
The sample rate used by the dongle. Legal values are 960000 and 2400000
(Default: 960000).
.TP
.B FQ_CORR
This is probably the most important configuration variable. Most dongles are
far off in frequency so they need to be calibrated. How to do this is out of
scope for this document.

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.
.TP
.B CENTER_FQ
The frequency, in Hz, that the wideband tuner should be placed at. This
configuration variable should normally be left unset since SvxLink will try to
place the wideband tuner to cover all set up Ddr frequencies. SvxLink will also
try to avoid placing a Ddr on the center frequency of the wideband spectrum
since there is usually some noise there. Only use this configration variable
if you need to override the automatic placement for some reason.
.TP
.B 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 distorsion. One way to
decide the maximum usable gain is to use the PEAK_METER explained below.  When
there are no distorsion 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.
.TP
.B PEAK_METER
If PEAK_METER is set to 1, a warning will be printed every time the tuner is
driven into distorsion. If it happens too often the gain should be lowered.  At
most, one warning per second will be printed.
.
.SS 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
.BR Voter .
.TP
.B TYPE
Always "Voter" for a voter.
.TP
.B RECEIVERS
Specify a comma separated list of receivers that the voter should use. Example:
RECEIVERS=Rx1,Rx2,Rx3
.TP
.B VOTING_DELAY
Specify the delay in milliseconds that the voter will wait after the first
sqeulch 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 noticeble when using
a repeater logic. Use the BUFFER_LENGTH configuration variable to adjust the
buffer length.
The default voting delay is 0.
.TP
.B 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.
.TP
.B 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.
.TP
.B 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.
.TP
.B 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.
.TP
.B 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.
.
.SS 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
.BR 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
.BR remotetrx (1)
manual page.
.TP
.B TYPE
Always "Net" for a networked receiver.
.TP
.B HOST
The hostname or IP address of the remote receiver host.
.TP
.B 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.
.TP
.B CODEC
The audio codec to use when transfering audio from this remote receiver.
Available codecs are: RAW (512kbps), S16 (256kbps), GSM (13.2kbps), SPEEX
(8-25kbps), OPUS (8-64kbps). These are raw bitrate values. There will be some
overhead added to this so the real bitrates 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 bitrate.
.TP
.B SPEEX_ENC_FRAMES_PER_PACKET
Speex encoder setting. Each Speex frame contains 20ms audio. If using a low
bitrate 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.
.TP
.B SPEEX_ENC_QUALITY
Speex encoder setting. Specify the encoder quality using a number between 0-10.
Lower values give poorer quality and lower bitrates.
.TP
.B SPEEX_ENC_BITRATE
Speex encoder setting. Specify the bitrate to use. Speex will snap to the
nearest lower possible bitrate. Possible values range from 2150 to 24600 bps.
You should probably not specify quality at the same time as bitrate. Not sure
though...
.TP
.B 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").
.TP
.B SPEEX_ENC_VBR
Speex encoder setting. Enable (1) or disable (0) variable bitrate encoding. If
enabled, the encoder will try to keep a constant quality by increasing the
bitrate when needed.
.TP
.B SPEEX_ENC_VBR_QUALITY
Speex encoder setting. The quality (0-10) to use in variable bitrate mode.
.TP
.B SPEEX_ENC_ABR
Speex encoder setting. The average bitrate encoding will try to keep a target
bitrate by continously adjusting the quality. This configuration variable
specify the target bitrate and enable ABR. It also need to have VBR enabled so
don't force it to off.
.TP
.B 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).
.TP
.B OPUS_ENC_FRAME_SIZE
Opus encoder setting. Specify how large, in milliseconds, each audio packet
should be. Default: 20ms.
.TP
.B 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.
.TP
.B OPUS_ENC_BITRATE
Opus encoder setting. This is the bitrate 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.
.TP
.B OPUS_ENC_VBR
Opus encoder setting. Enable (1) or disable (0) variable bitrate encoding. If
enabled, the encoder will try to keep a constant quality by increasing the
bitrate when needed and decrease it when the quality can be assured with a
lower bitrate. The target average bitrate is the one set by OPUS_ENC_BITRATE.
Default: 1.
.
.SS 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
.BR 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.
.TP
.B TYPE
Always "Local" for a local transmitter.
.TP
.B AUDIO_DEV
Specify the audio device to use. Normally alsa:plughw:0. Have a look at the
AUDIO DEVICE SPECIFICATIONS chapter for more information.
.TP
.B 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.
.TP
.B 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" 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".
.TP
.B PTT_PORT
Specify the serial port that the PTT is connected to. E.g. /dev/ttyS0 for COM1.
.TP
.B 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.
.TP
.B 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.
.TP
.B HID_DEVICE
Define the device node where your hidraw device is accessible at.

Example: HID_DEVICE=/dev/hidraw3
.TP
.B 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 behaviour with a "!" in 
front of the name. Only one value is supported.
.TP
.B 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.
.TP
.B 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.
.TP
.B 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 indefinately. It is not meant to
be used to keep people from talking too long. 
.TP
.B 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.
.TP
.B 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.
.TP
.B CTCSS_LEVEL
The level in percent (0-100) of the CTCSS tone to transmit. What level to set is
hard to say. The FM modulation swing of the tone should be in between 500-800
Hz. That is a bit hard to measure if you don't have the right equipment. A
normal FM station have a maximum swing of 5kHz so if you manage to calibrate
everything so that you get maximum swing when the sound card audio is at peak
level, the tone level should be in between 10-16%. However, most often the audio
settings are configured a bit higher than max since the audio seldom reaches
maximum level. Then the level of the CTCSS tone should be reduced. The default
in the configuration file is 9%. For the tone to be transmitted the CTCSS_FQ
variable must also be setup and also the TX_CTCSS variable in the logic core
configuration section.
.TP
.B PREEMPHASIS
[EXPERIMENTAL] 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.
.TP
.B DTMF_TONE_LENGTH
The duration, in milliseconds, of DTMF digits transmitted on this transmitter.
100ms is the default.
.TP
.B DTMF_TONE_SPACING
The spacing, in milliseconds, between DTMF digits transmitted on this
transmitter. 50ms is the default.
.TP
.B 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.
.TP
.B 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.
.TP
.B 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.
.TP
.B 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.
.
.SS 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
.BR 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
.BR remotetrx (1)
manual page.
.TP
.B TYPE
Always "Net" for a networked transmitter.
.TP
.B HOST
The hostname or IP address of the remote transmitter host.
.TP
.B 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.
.TP
.B CODEC
The audio codec to use when transfering audio to this remote transmitter.
Available codecs are: RAW (512kbps), S16 (256kbps), GSM (13.2kbps), SPEEX
(8-25kbps), OPUS (8-64kbps). These are raw bitrate values. There will be some
overhead added to this so the real bitrates 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 bitrate. 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.
.TP
.B SPEEX_ENC_FRAMES_PER_PACKET
Speex encoder setting. Each Speex frame contains 20ms audio. If using a low
bitrate 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.
.TP
.B SPEEX_ENC_QUALITY
Speex encoder setting. Specify the encoder quality using a number between 0-10.
Lower values give poorer quality and lower bitrates.
.TP
.B SPEEX_ENC_BITRATE
Speex encoder setting. Specify the bitrate to use. Speex will snap to the
nearest lower possible bitrate. Possible values range from 2150 to 24600 bps.
You should probably not specify quality at the same time as bitrate. Not sure
though...
.TP
.B 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").
.TP
.B SPEEX_ENC_VBR
Speex encoder setting. Enable (1) or disable (0) variable bitrate encoding. If
enabled, the encoder will try to keep a constant quality by increasing the
bitrate when needed.
.TP
.B SPEEX_ENC_VBR_QUALITY
Speex encoder setting. The quality (0-10) to use in variable bitrate mode.
.TP
.B SPEEX_ENC_ABR
Speex encoder setting. The average bitrate encoding will try to keep a target
bitrate by continously adjusting the quality. This configuration variable
specify the target bitrate and enable ABR. It also need to have VBR enabled so
don't force it to off.
.TP
.B 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).
.TP
.B OPUS_ENC_FRAME_SIZE
Opus encoder setting. Specify how large, in milliseconds, each audio packet
should be. Default: 20ms.
.TP
.B 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.
.TP
.B OPUS_ENC_BITRATE
Opus encoder setting. This is the bitrate 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.
.TP
.B OPUS_ENC_VBR
Opus encoder setting. Enable (1) or disable (0) variable bitrate encoding. If
enabled, the encoder will try to keep a constant quality by increasing the
bitrate when needed and decrease it when the quality can be assured with a
lower bitrate. The target average bitrate is the one set by OPUS_ENC_BITRATE.
Default: 1.
.
.SS Multi Transmitter Section
.
A multi transmitter section is used if one wants to transmit on multiple
transmitters simulaneously. 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.
.TP
.B TYPE
Always "Multi" for a multi transmitter section.
.TP
.B TRANSMITTERS
A comma separated list of transmitters.
.
.SS 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.
.TP
.B 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. 
.TP
.B 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. 
.TP
.B ID
Specify the module identification number. This is the number used to access the module
from the radio interface. 
.TP
.B TIMEOUT
Specify the timeout time, in seconds, after which a module will be automatically
deactivated if there has been no activity.
.P
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
.BR ModuleParrot.conf (5)
manual page.
.
.SS LocationInfo
.
.TP
.B 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 http://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:
.br
STATUS_SERVER_LIST=aprs.echolink.org:5199
.TP
.B 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
http://aprs.fi/.

To choose a suitable APRS server from the so called tier 2 network, have a
look at http://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 - Austrailia and New Zeeland.
The format is a space separated list of host:port entries. Host - hostname
or IP address, port - TCP port.

Example:
.br
APRS_SERVER_LIST=euro.aprs2.net:14580
.TP
.B LON_POSITION
The longitude of the station position, entered as "degrees.arcminutes.arcseconds"

Example:
.br
LON_POSITION=09.02.20E
.TP
.B LAT_POSITION
The latitude of the station position, entered as "degrees.arcminutes.arcseconds"

Example:
.br
LAT_POSITION=51.02.22N
.TP
.B CALLSIGN
Enter your callsign for the APRS network with a prefix that indicates the type 
of station, (ER- for repeaters, EL- for links).

Examples:
.br
CALLSIGN=EL-DL1ABC    # callsign for a link
.br
CALLSIGN=ER-DB0ABC    # callsign for a repeater
.TP
.B FREQUENCY
The tx-frequency of the link/repeater in MHz. For repeaters, information about
the RX/TX shift in the COMMENT configuration variable may be useful.

Example:
.br
FREQUENCY=430.050     # tx-frequency is 430.050 MHz
.TP
.B TX_POWER
The power of your transmitter in watts.

Example:
.br
TX_POWER=10           # tx output is 10 watts
.TP
.B ANTENNA_GAIN
The gain of your antenna in dBd.

Example:
.br
ANTENNA_GAIN=5        # antenna gain is 5 dBd
.TP
.B ANTENNA_HEIGHT
The height of the link-/repeater antenna in meters or feet above the terrain,
not sealevel.

Example:
.br
ANTENNA_HEIGHT=10m    # 10 meters above the ground
.br
ANTENNA_HEIGHT=90     # 90 feet
.TP
.B ANTENNA_DIR
Main beam direction of the antenna in degrees. If an omni direction antenna is
used, specify -1 as the direction.

Example:
.br
ANTENNA_DIR=-1        # an omni directional antenna is used
.br
ANTENNA_DIR=128       # main beam direction is 128 degrees
.TP
.B PATH
The PATH variable controls the way of forwarding your beacon inside the APRS
network if it is gated by a local APRS digipeater. 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. Leave this variable untouched if you are unsure of its setting.
No spaces or control characters are allowed. PATH has no influence on the
propagation on non-RF networks.

Examples:
.br
PATH=WIDE1-1
.br
PATH=WIDE1-1,WIDE2-2
.TP
.B 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, please 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:
.br
BEACON_INTERVAL=30    # APRS-beacons will be sent every 30 minutes.
.TP
.B TONE
The CTCSS subaudible 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:
.br
TONE=136      # we are using a CTCSS-tone of 136.5 Hz
.br
TONE=0        # we don't use CTCSS subaudible or call tones
.br
TONE=1750     # the link/repeater use a tone burst of 1750 Hz
.TP
.B STATISTICS_INTERVAL
Defines the interval in minutes in that a aprs statistic is sent into the aprs 
network. Range: 5-60, default is 10 minutes
.TP
.B COMMENT
Specify a short comment here, maybe a link to your website
or information that could be interesting for others. The length should not
exceed 255 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:
.br
COMMENT=[svx] Running SvxLink by SM0SVX
.TP
.B 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.
.
.SH 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.
.
.SH 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. The example below
will set up pin 31 as an output for PTT use and pin 30 is used as input for
squelch. Make sure that the commands are run as user root.

  Enable the PTT pin for GPIO:
  echo 31 > /sys/class/gpio/export

  Set the direction to output for the pin:
  echo out > /sys/class/gpio/gpio31/direction

  Make sure that the svxlink user can write to the GPIO pin:
  chown svxlink /sys/class/gpio31/value

  Enable the squelch pin for GPIO:
  echo 30 > /sys/class/gpio/export

  Set the direction to input for the pin:
  echo in > /sys/class/gpio/gpio30/direction

  Make sure that the svxlink user can read from the GPIO pin:
  chown svxlink /sys/class/gpio30/value

These steps have to be performed whenever the system is rebooted. Putting the
commands in a script is recommended.
.
.SH 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.
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 exakt but that does not matter.

The calibration is normally done by using the
.BR 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.
.B 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_OFFSET config 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.
.B Note:
To calibrate a remote receiver it must be connected to the SvxLink server.
Otherwise the squelch will not open.
.RS
.IP 1 4
Connect a dummy load or disconnect the antenna from the transceiver. If you
disconnect the antenna, make sure to also disconnect the PTT.
.IP 2 4
Set SIGLEV_SLOPE=1 and SIGLEV_OFFSET=0 and restart SvxLink.
.IP 3 4
Open the squelch so that there is only noise coming into SvxLink.
.IP 4 4
Use a second transceiver to make a short, unmodulated transmission. Release the
PTT when the "Squech OPEN" message is printed. Repeat this for about five times.
.IP 5 4
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.
.IP 6 4
SIGLEV_SLOPE = 100 / (mean diff)
.IP 7 4
SIGLEV_OFFSET = - (mean lower) * SIGLEV_SLOPE
.IP 8 4
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.
.
.SH STATE PTY FORMAT
.
The format of the output from the state PTY is:
.PP
.RS 4
<timestamp> <context>:<event name> <event data>

.RS -4
where the different parts mean:
.PP
.RS 4
timestamp = <seconds since 1 jan 1970>.<milliseconds>
.RS 0
context = Name of context
.RS 0
event_name = Name of event
.RS 0
event data = Event specific data

.RS -4

The following specific events exist.
.TP
.B Voter:sql_state
Report the state of all squelches for all receivers. The format of the event
specific data is:
.PP
.RS 11
<rx name><state><siglev> [<rx_name><state><siglev> ...]

.RS -4
where the different parts mean:
.PP
.RS 4
rx_name = Configuration file section name for receiver
.RS 0
state = _ (sql closed), : (sql open), * (sql open and rx selected)
.RS 0
siglev = The measured signal level

.RS -4
.
.SH FILES
.
.TP
.IR /etc/svxlink/svxlink.conf " (or deprecated " /etc/svxlink.conf ")"
The system wide configuration file.
.TP
.IR ~/.svxlink/svxlink.conf
Per user configuration file.
.TP
.I /etc/svxlink/svxlink.d/*
Additional configuration files. Typically one configuration file per module.
.
.SH AUTHOR
.
Tobias Blomberg (SM0SVX) <sm0svx at users dot sourceforge dot net>
.
.SH "SEE ALSO"
.
.BR svxlink (1),
.BR remotetrx (1),
.BR siglevdetcal (1)