Provided by: isdnutils-base_3.12.20071127-0ubuntu2_i386 bug

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 preceeded 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

       Fritz Elfert <fritz@isdn4linux.de>

SEE ALSO

       ttyI(4).