asterisk/configs/samples/phone.conf.sample

;
; Linux Telephony Interface
;
; Configuration file
;
[interfaces]
;
; Select a mode, either the phone jack provides dialtone, reads digits,
; then starts PBX with the given extension (dialtone mode), or
; immediately provides the PBX without reading any digits or providing
; any dialtone (this is the immediate mode, the default).  Also, you
; can set the mode to "fxo" if you have a linejack to make it operate
; properly. If you are using a Sigma Designs board you may set this to
; "sig".
;
mode=immediate
;mode=dialtone
;mode=fxo
;mode=sig
;
; You can decide which format to use by default, "g723.1", "g729", or "slinear".
; Note that g729 is only supported for Sigma Designs boards.
; XXX Be careful, sometimes the card causes kernel panics when running
; in signed linear mode for some reason... XXX
;
format=slinear
;format=g723.1
;format=g729
;
; And set the echo cancellation to "off", "low", "medium", and "high".
; This is not supported on all phones.
;
echocancel=medium
;
; You can optionally use VAD/CNG silence suppression
;
;silencesupression=yes
;
; List all devices we can use.  Contexts may also be specified
;
;context=local
;
; You can set txgain and rxgain for each device in the same way as context.
; If you want to change default gain value (1.0 =~ 100%) for device, simple
; add txgain or rxgain line before device line. But remember, if you change
; volume all cards listed below will be affected by these values. You can
; use float values (1.0, 0.5, 2.0) or percentage values (100%, 150%, 50%).
;
;txgain=100%
;rxgain=1.0
;device => /dev/phone0