system.conf. DAHDI Configuration File

This file is parsed by the DAHDI Configurator, dahdi_cfg

Span Configuration

First come the span definitions, in the format

span=<span num>,<timing source>,<line build out (LBO)>,<framing>,<coding>[,yellow]

All T1/E1 spans generate a clock signal on their transmit side. The <timing source> parameter determines whether the clock signal from the far end of the T1/E1 is used as the master source of clock timing. If it is, our own clock will synchronise to it. T1/E1’s connected directly or indirectly to a PSTN provider (telco) should generally be the first choice to sync to. The PSTN will never be a slave to you. You must be a slave to it.

Choose 1 to make the equipment at the far end of the E1/T1 link the preferred source of the master clock.
Choose 2 to make it the second choice for the master clock, if the first choice port fails (the far end dies, a cable breaks, or whatever).
Choose 3 to make a port the third choice, and so on. If you have, say, 2 ports connected to the PSTN, mark those as 1 and 2. The number used for each port should be different.

If you choose 0, the port will never be used as a source of timing. This is appropriate when you know the far end should always be a slave to you. If the port is connected to a channel bank, for example, you should always be its master. Any number of ports can be marked as 0.

Incorrect timing sync may cause clicks/noise in the audio, poor quality or failed faxes, unreliable modem operation, and is a general all round bad thing.

The line build-out (or LBO) is an integer, from the following table:

0: 0 db (CSU) / 0-133 feet (DSX-1)
1: 133-266 feet (DSX-1)
2: 266-399 feet (DSX-1)
3: 399-533 feet (DSX-1)
4: 533-655 feet (DSX-1)
5: -7.5db (CSU)
6: -15db (CSU)
7: -22.5db (CSU)

framing:
One of ‘d4’ or ‘esf’ for T1 or ‘cas’ or ‘ccs’ for E1 and BRI.
‘d4’ could be referred to as ‘sf’ or ‘superframe’

coding:
one of ‘ami’ or ‘b8zs’ for T1 or ‘ami’ or ‘hdb3’ for E1 and BRI.
* For E1 there is the optional keyword ‘crc4’ to enable CRC4 checking.
* If the keyword ‘yellow’ follows, yellow alarm is transmitted when no channels are open.

span=1,0,0,esf,b8zs
span=2,1,0,esf,b8zs
span=3,0,0,ccs,hdb3,crc4

Dynamic Spans

Next come the dynamic span definitions, in the form:

dynamic=<driver>,<address>,<numchans>,<timing>

Where <driver> is the name of the driver (e.g. eth), <address> is the driver specific address (like a MAC for eth), <numchans> is the number of channels, and <timing> is a timing priority, like for a normal span. use “0” to not use this as a timing source, or prioritize them as primary, secondary, etc. Note that you MUST have a REAL DAHDI device if you are not using external timing.

dynamic=eth,eth0/00:02:b3:35:43:9c,24,0

If a non-zero timing value is used, as above, only the last span should have the non-zero value.

Channel Configuration

Next come the definitions for using the channels. The format is: <device>=<channel list>

Valid devices are:

e&m: Channel(s) are signalled using E&M signalling, besides specifying the channels, alternatively you can specify e1 (i.e. e&m=e1) for use with e1 channels in México (specific implementation, such as Immediate, Wink, or Feature Group D are handled by the userspace library).
fxsls: Channel(s) are signalled using FXS Loopstart protocol
fxsgs: Channel(s) are signalled using FXS Groundstart protocol.
fxsks: Channel(s) are signalled using FXS Koolstart protocol.
fxols: Channel(s) are signalled using FXO Loopstart protocol.
fxogs: Channel(s) are signalled using FXO Groundstart protocol.
fxoks: Channel(s) are signalled using FXO Koolstart protocol.
sf: Channel(s) are signalled using in-band single freq tone.

Syntax as follows:

channel; => sf:<rxfreq>,<rxbw>,<rxflag>,<txfreq>,<txlevel>,<txflag>

rxfreq is rx tone freq in Hz, rxbw is rx notch (and decode) bandwith in hz (typically 10.0), rxflag is either ‘normal’ or ‘inverted’, txfreq is tx tone freq in hz, txlevel is tx tone level in dbm, txflag is either ‘normal’ or ‘inverted’. Set rxfreq or txfreq to 0.0 if that tone is not desired.

unused: No signalling is performed, each channel in the list remains idle
clear: Channel(s) are bundled into a single span. No conversion or signalling is performed, and raw data is available on the master.
bchan: Like ‘clear’ except all channels are treated individually and are not bundled. ‘inclear’ is an alias for this.
rawhdlc: The DAHDI driver performs HDLC encoding and decoding on the bundle, and the resulting data is communicated via the master device.
dchan: The DAHDI driver performs HDLC encoding and decoding on the bundle and also performs incoming and outgoing FCS insertion and verification. ‘fcshdlc’ is an alias for this.
hardhdlc: The hardware driver performs HDLC encoding and decoding on the bundle and also performs incoming and outgoing FCS insertion and verification. Is subject to limitations and support of underlying hardware.
nethdlc: The DAHDI driver bundles the channels together into an hdlc network device, which in turn can be configured with sethdlc (available separately). In 2.6.x kernels you can also optionally pass the name for the network interface after the channel list.

Syntax:

nethdlc=<channel list>[:interface name]
Use original names, don’t use the names which have been already registered in system e.g eth.

dacs: The DAHDI driver cross connects the channels starting at the channel number listed at the end, after a colon
dacsrbs: The DAHDI driver cross connects the channels starting at the channel number listed at the end, after a colon and also performs the DACSing of RBS bits

The channel list is a comma-separated list of channels or ranges, for example:

1,3,5 (channels one, three, and five)
16-23, 29 (channels 16 through 23, as well as channel 29)

So, some complete examples are:

e&m=1-12
nethdlc=13-24
fxsls=25,26,27,28
fxols=29-32
e&m=e1
fxoks=1-24
bchan=25-47
dchan=48
fxols=1-12
fxols=13-24
e&m=25-9
nethdlc=30-33
clear=44
clear=45
clear=46
clear=47
fcshdlc=48
dacs=1-24:48
dacsrbs=1-24:48

Tone Zone Data

Finally, you can preload some tone zones, to prevent them from getting overwritten by other users (if you allow non-root users to open /dev/dahdi/* interfaces anyway. Also this means they won’t have to be loaded at runtime.
The format is “loadzone=<zone>” where the zone is a two letter country code.

You may also specify a default zone with “defaultzone=<zone>” where zone is a two letter country code.

An up-to-date list of the zones can be found in the file zonedata.c

loadzone = us
loadzone = us-old
loadzone=gr
loadzone=it
loadzone=fr
loadzone=de
loadzone=uk
loadzone=fi
loadzone=jp
loadzone=sp
loadzone=no
loadzone=hu
loadzone=lt
loadzone=pl
defaultzone=us

PCI Radio Interface

(see http://www.zapatatelephony.org/app_rpt.html)

The PCI Radio Interface card interfaces up to 4 two-way radios (either a base/mobile radio or repeater system) to DAHDI channels. The driver may work either independent of an application, or with it, through the driver;s ioctl() interface. This file gives you access to specify load-time parameters for Radio channels, so that the driver may run by itself, and just act like a generic DAHDI radio interface.

Unlike the rest of this file, you specify a block of parameters, and then the channel(s) to which they apply. CTCSS is specified as a frequency in tenths of hertz, for example 131.8 HZ is specified as 1318. DCS for receive is specified as the code directly, for example 223. DCS for transmit is specified as D and then the code, for example D223.

The hardware supports a “community” CTCSS decoder system that has arbitrary transmit CTCSS or DCS codes associated with them, unlike traditional “community” systems that encode the same tone they decode.

This example is a single tone DCS transmit and receive

Specify the transmit tone (in DCS mode this stays constant):
tx=D371

Specify the receive DCS code:
dcsrx=223

This example is a “community” CTCSS (if you only want a single tone, then only specify 1 in the ctcss list)

Specify the default transmit tone (when not receiving):
tx=1000

Specify the receive freq, the tag (use 0 if none), and the transmit code. The tag may be used by applications to determine classification of tones. The tones are to be specified in order of presedence, most important first. Currently, 15 tones may be specified..

ctcss=1318,1,1318
ctcss=1862,1,1862

The following parameters may be omitted if their default value is acceptable

Set the receive debounce time in milliseconds:
debouncetime=123

Set the transmit quiet dropoff burst time in milliseconds:
bursttime=234

Set the COR level threshold (specified in tenths of millivolts)
valid values are {3125,6250,9375,12500,15625,18750,21875,25000}
corthresh=12500

Invert COR signal {y,n}
invertcor=y
Set the external tone mode; yes, no, internal {y,n,i}
exttone=y

Now apply the configuration to the specified channels:

We are all done with our channel parameters, so now we specify what
channels they apply to
channels=1-4

Overiding PCM encoding

Usually the channel driver sets the encoding of the PCM for the channel (mulaw / alaw. That is: g711u or g711a). However there are some cases where you would like to override that. ‘mulaw’ and ‘alaw’ set different such encoding. Use them for channels you have already defined with e.g. ‘bchan’ or ‘fxoks’.
mulaw=1-4
alaw=1-4

‘deflaw’ is similar, but resets the encoding to the channel driver’s default. It must be useful for something, I guess.
mulaw=1-10
deflaw=5

Echo Cancellers

DAHDI uses modular echo cancellers that are configured per channel. The echo cancellers are compiled and installed as part of the dahdi-linux package.You can specify in this file the echo canceller to be used for each channel. The default behavior is for there to be NO echo canceller on any channel, so it is very important that you specify one here if you do not have hardware echo cancellers and need echo cancellation.

Valid echo cancellers are: mg2, kb1, sec2, and sec.
If compiled, ‘hpec’ is also a valid echo canceller.

To configure the default echo cancellers, use the format:
echocanceller=<echocanceller name>,<channel(s)>

Example:
Configure channels 1 through 8 to use the mg2 echo canceller
echocanceller=mg2,1-8

And change channel 2 to use the kb1 echo canceller.
echocanceller=kb1,2