Ubuntu Manpage: isdn_audio - audio extension of ttyI ISDN character devices

Provided by: isdnutils-base_3.25+dfsg1-9ubuntu3_amd64

NAME

       isdn_audio - audio extension of ttyI ISDN character devices

DESCRIPTION

       This document describes the audio related extensions of the modem emulation, provided by /dev/ttyIx.

       The  ISDN  tty  devices  are  equipped  with a modem emulation implementing a set of traditional and some
       special AT commands. This provides easy use together with almost all  communication  software  that  uses
       modem  commands:  minicom(1),  seyon(1),  XCept(1),  uucico(8), mgetty(8), dip(8), pppd(8) and more. When
       enabled during kernel configuration, the emulator is capable of a reduced  set  of  commands  to  support
       audio. To use audio features, an ISDN card with a audio-capable low-level driver is needed. Currently the
       only audio-capable drivers are the teles and HiSax driver.

       The port speed of the ISDN tty devices is always 64000 bps.

AUDIO RELATED AT COMMAND SET

       This  description  does  not  include  the  standard AT command set. For a description of the standard AT
       command set, provided by the Linux ISDN subsystem, see ttyI(4).  All commands starting  with  AT+  except
       AT+FCLASS  are  enabled  only,  if  audio  mode  is  active.  The following audio related AT commands are
       supported by ISDN tty devices:

       AT+FCLASS=0
              Disable audio mode (default). This command sets register 18 to 4.

       AT+FCLASS=8
              Enable audio mode. This command sets register 18 to 5.

       AT+FCLASS=?
              Show possible modes.

       AT+FCLASS?
              Show current mode.

       AT+VNH=x
              No function, provided for compatibility only.

       AT+VNH=?
              Always showing "1".

       AT+VNH?
              Always showing "1".

       AT+VIP Reset all audio parameters.

       AT+VLS=x
              Select line x, where x is one of the following:
              0 = No device.
              2 = Phone line.

       AT+VLS=?
              Always showing "0,2".

       AT+VLS?
              Show current line.

       AT+VRX Start audio recording. See below for more information.

       AT+VSD=x,y
              Set silence-detection parameters.
              Possible parameters:
              x = 0 ... 31  sensitivity threshold level.
              (default 0 , deactivated)
              y = 0 ... 255 range of interval in units of 0.1 second. (default 70)

       AT+VSD=?
              Show possible parameters.

       AT+VSD?
              Show current parameters.

       AT+VSM=x
              Select audio data format to x, where x is:
              2 = ADPCM-2
              3 = ADPCM-3
              4 = ADPCM-4
              5 = aLAW
              6 = uLAW

       AT+VSM=?
              Show possible audio data formats.

       AT+VSM?
              Show current audio data format.

       AT+VTX Start audio playback. See below for more information.

GENERAL BEHAVIOUR

       On incoming calls, if the application responds to a  RING  by  sending  ATA,  depending  on  the  calling
       service, the emulator responds with either CONNECT (data call) or VCON (voice call).

       When  starting  audio  playback  or  recording, the emulator responds with CONNECT.  After that, the data
       transfer  protocol described below is used.  It is possible to initiate  full  duplex  data  transfer  by
       issuing  AT+VRX+VTX  in a single command. In this case, no CONNECT message is sent to the application and
       the protocol described below is started immediately.

       When stopping audio playback or recording, the message returned by the emulator depends on how  the  data
       transfer  is  stopped.  If  the  data  transfer  is stopped by a remote hangup, NO CARRIER is sent to the
       application, while stopping data transfer with one of the DLE sequences, VCON is sent. In any  case,  the
       message is preceded by the appropriate DLE sequence for end of audio data and/or abort respectively.

       On outgoing voice calls, the emulator responds with VCON upon connection setup.

AUDIO DATA FORMAT

When recording or playing back audio data, a kind of modified bisync protocol is used. When recording
audio data, the modem emulator is considered to be the sender, while the application is the receiver.
When playing back, this relationship is reversed: The modem emulator acts as receiver, while the
application is the sender. With the bisync protocol the character DLE (0x10) has a special meaning and
is used like an escape character. It is always followed by a second character which has the following
meanings defined:

ETX (0x03)
End of audio data. This code has to be sent by the sender, indicating end of audio data.

DC4 (0x14)
Abort sending. This code has to be sent by the receiver, when it wishes to abort receiving data.
The sender has to reply by stop sending data and finally indicating end of audio data.

DLE (0x10)
a single byte with value 0x10 in the data stream.

0 Touch-tone "0" received. Valid only in direction from emulator to application.

1 Touch-tone "1" received. Valid only in direction from emulator to application.

2 Touch-tone "2" received. Valid only in direction from emulator to application.

3 Touch-tone "3" received. Valid only in direction from emulator to application.

4 Touch-tone "4" received. Valid only in direction from emulator to application.

5 Touch-tone "5" received. Valid only in direction from emulator to application.

6 Touch-tone "6" received. Valid only in direction from emulator to application.

7 Touch-tone "7" received. Valid only in direction from emulator to application.

8 Touch-tone "8" received. Valid only in direction from emulator to application.

9 Touch-tone "9" received. Valid only in direction from emulator to application.

# Touch-tone "#" received. Valid only in direction from emulator to application.

* Touch-tone "*" received. Valid only in direction from emulator to application.

A Touch-tone "A" received. Valid only in direction from emulator to application.

B Touch-tone "B" received. Valid only in direction from emulator to application.

C Touch-tone "C" received. Valid only in direction from emulator to application.

D Touch-tone "D" received. Valid only in direction from emulator to application.

AUTHOR