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fxotune - Man Page

automatically tune DAHDI FXO channels


fxotune -i [options] - detect mode

fxotune -d [ options ] - dump mode

fxotune -s [ options ] - Startup mode


fxotune is a script that fine-tune parameters of the FXO modules of the  card. It has three modes of operation:

Detect mode (-i): it detects and tunes all the available FXO channels. It writes settings to a configuration file (/etc/fxotune.conf) from which it can be loaded (e.g: at startup) using -s .

Dump mode (-d): Runs detection on a single DAHDI channel, and just dumps waveforms to fxotune_dump.vals is generated in the current directory.

Startup mode (-s): fxotune just reads the settings from fxotune.conf into the FXO modules.

You are advised to run fxotune on all FXO ports you have that support  it and that are connected. Note that the tunning is affected by e.g. the physical parameters of the connection, and thus if it has been  radically changed, you may need to re-run fxotune.

This program only works for the Digium TDM400P/800P/2400P cards and compatible and the Xorcom Astribank devices. Other cards (notably X100P cards and clones) do not have the hardware to support such tuning.

The tuning process needs a clear line to do the tuning.  In order to do that, it runs in cycles of the following: sets the line off-hook, dials a dial string (which should set the PSTN provider waiting for the next digit), and then starts tuning. It has a limited ammount of time for tuning before the PSTN gives up and gives a busy tone. So after a while it hangs up and starts a new cycle.

fxotune has two operation modes: tune (-i) and set (-s). In the tune mode it  generates /etc/fxotune.conf, and in the set mode it merely applies the  parameters from fxotune.conf to device's ports.


The following options below except -v (verbose) affect only the detection process and hence apply only to the detect and dump modes.

In addition, to maintain compatibility with older versions of fxotune, if in detect or dump mode there is a parameter with option before it, it is considered to be the dialstring parameter (-n).

-b startdev

Start tuning from dahdi channel num. startdev: skip all previous channels. By default starting from channel 1.

In dump mode (-d) this is the single channel that will be tested.

-e stopdev

Tune only up to dahdi channel num. stopdev: skip all previous channels. By default stopping at channel 252.

In dump mode (-d) this parameter is ignored.

-l delay-to-silence

Time in seconds to wait after dialing the dial-string to get a clear line. The default is 0.  before

-m silence-good-for

Time in seconds which states how long the PSTN will wait after we dialed the dial-string until it starts giving a busy tone. You can test this by connecting an analog phone to the line and dialing.

The default is 18 (18 seconds).

-n dial-string

Digits to dial to the PSTN in order to get it stop its dialtone and waiting for the next digit.

The default is "4" (sending just the digit 4). It should work in most cases. Again, this can be tested by connecting a phone to the PSTN line and dialing the dial-string.

-t detect-type

This option allows using the older detection method used by fxotune of Zaptel 1.2. use -t 1 for that older method. whereas -t 2 (the default) uses the current method.

This option only applies to detect mode (-i).


Sets debugging on. The more v-s, the higher debug level.

Note that: -vv -v  will actually set debug level to 1 instead of 3.

-w wave-form

The default: -1, for multitone waveform. Alternatively: a frequency of a single tone.

This option only applies to dump mode (-d).


fxotune -i 9

if you need to dial 9 for an external line. If you always get a line, you can simply use any digit.


Load settings from the last test. Used at startup.



The configuration file generated by fxotune in detect mode and from which configuration is loaded when -s is used.


Running fxotune takes approximately a minute per port. If you wish to only  run fxotune for several ports, you can use the options -b and -e to set a  specific range of ports. Another useful trick is to actually keep asterisk  running, and only "destroy" the dahdi channels you wish to tune (dahdi  destroy channel NNN): other channels will be used by Asterisk, and hence  skipped. This can be useful if you have many FXO ports that are not connected.

fxotune writes immediately to /etc/fxotune.conf so if you stop it half-way, you may get a half-configured system. If you have already tuned your FXO channels and wish to test-run fxotune again,  you are advised to backup /etc/fxotune.conf .

The default for -m is 18 seconds. This asusmes that you get a clear line  for at least 18 seconds. It is advised that you test that timeout earlier by connecting a phone to the FXO line, dialing 4 (or whatever dial string  you put with -n) and see how much time of silence you have.

If you connect your device to a PSTN provider that is not in the US, there is a similar operation you should apply before even getting to fxotune: setting the opermode. The opermode sets a number of country-specific  parameters. For the Digium analog cards this is set through the kernel module  parameter 'opermode' . For the Xorcom Astribank this is set through the  variable 'opermode' in /etc/dahdi/xpp.conf . For valid values of this parameter, see /usr/share/asterisk/init_fxo_modes (FIXME: this has changed and will change. Tzafrir).

See Also

dahdi_cfg(8), dahdi_tool(8), dahdi_monitor(8), asterisk(8).


This manual page was written by Tzafrir Cohen <tzafrir.cohen@xorcom.com>  Permission is granted to copy, distribute and/or modify this document under  the terms of the GNU General Public License, Version 2 any   later version published by the Free Software Foundation.

On Debian systems, the complete text of the GNU General Public  License can be found in /usr/share/common-licenses/GPL.


9 June 2007 System Manager's Manuals: Asterisk