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       ttyI - ISDN character devices with modem emulator


       ttyI[0-63] are emulated tty devices of the Linux ISDN subsystem.  These
       devices can be used in the same way as the traditional  serial  devices
       ttySx.   The official major device numbers are 43 for ttyI .  The minor
       device numbers start with 0 and end with 63.

       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 line disciplines are handled by the kernel so that SLIP, CSLIP  and
       asynchronous PPP are possible.

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


       The  description  of  AT  commands  here  does  not cover audio related
       commands.  For  a  description   of   audio   related   commands,   see
       isdn_audio(4).   The  following  AT  commands are supported by ISDN tty

       ATA    Answer an incoming call.

       ATDnum Dial number num.  Allowed are digits [0-9]  and  the  characters
              ",",  "#", ".", "*", "W", "P", "T", "S", "-". The characters are
              ignored except of "S" which indicates a SPV if it  precedes  the
              number (only German 1TR6 ISDN).

       ATE0   Echo off.

       ATE1   Echo on (default).

       ATH    Hang up.

       ATH0   Hang up.

       ATH1   Off hook (ignored).

       ATI    Return device Information ("ISDN for Linux...").

       ATI0   Return device Information ("ISDN for Linux...").

       ATI1   Return device Information ("ISDN for Linux...").

       ATI2   Return Statistics of last connection.

       ATO    Return from command mode to online mode (data mode).

       ATQ0   Enable result codes (default).

       ATQ1   Disable result codes.

       ATSx=y Set register x to value y.

       ATSx?  Show content of register x.

              Set register x, bit y to value z

              Show bit y of register x.

       ATV0   Print result code as number.

       ATV1   Print result code as text (default).

       ATZ    Reset all registers and load profile values.

       AT&Bx  Set  packet  size of outgoing packets to value x (maximum 4000).
              The actual packet size depends on the hardware driver and may be
              smaller  than  x  (e.g. with the teles driver). There will be no
              error message if the value is bigger than  the  hardware  driver
              can  process.  However  the size of the outgoing packets will be
              set correctly.

       AT&D2  DTR falling edge: hang up and return to command mode  (default).

       AT&D3  DTR  falling edge: hang up, return to command mode and reset all

       AT&Ex  Set MSN (Euro-ISDN, EDSS1) or EAZ (German 1TR6) to value x.  For
              MSNs,  x  is  a  string  of  digits representing the local phone
              number, while for EAZs x should be only the last  digit  of  the

       AT&F   Set all registers and profile to "factory-defaults".

              Set  list  of  phone  numbers  to listen on.  plist is a list of
              wildcard patterns separated by semicolon. If this is set, it has
              precedence over the MSN set by AT&E.

       AT&V   Show current register settings.

       AT&W0  Write  registers  and  EAZ/MSN  to  profile.  (You  need  to run
              iprofd(8) for making changes permanent.)

       AT&X0  Disable BTX-Mode (default).

       AT&X1  Enable BTX-Mode.


       During a data connection, the driver can be  set  to  command  mode  by
       typing in delay+++delay.  The escape character (default "+") may be set
       via register 2. The delay must be at least 1.5 seconds and between each
       escape character the pause must not exceed 0.5 seconds.  ATO brings the
       modem emulation back to data mode.


       0 (default 0)
              Number of rings on which the "modem"  will  answer.  (S0=0  will
              disable auto answering).

       1 (default 0)
              Counts and stores the number of rings from an incoming call.

       2 (default 43 = ’+’)
              ASCII code of the escape character.

       3 (default 13 = CR)
              ASCII code of Carriage Return.

       4 (default 10 = LF)
              ASCII code of Line Feed.

       5 (default 8 = BS)
              ASCII code of Backspace.

       6 (default 3)
              Duration, in number of seconds, modem waits before dialling.

       7 (default 60)
              Wait time for carrier in seconds.

       8 (default 2)
              Pause time for comma (’,’) in dial command in seconds (ignored).

       9 (default 6)
              Carrier detect time in tenths of seconds (ignored).

       10 (default 7)
              Wait time until hangup after carrier loss in tenths  of  seconds

       11 (default 70)
              Duration  and  delay  in  milliseconds  for  touch tone dialling

       12 (default 69)
              Bit-mapped register.
              Bit  Description
              0    0 = Suppress response messages.
                   1 = Show response messages.
              1    0 = Response messages as text.
                   1 = Numeric response messages.
              2    0 = Echo off.
                   1 = Echo on.
              3    0 = DCD always on.
                   1 = DCD follows carrier.
              4    0 = CTS follows RTS.
                   1 = Ignore RTS, CTS always on.
              5    0 = Low-edge on DTR: Hangup and return
                        to command mode.
                   1 = Same as 0 but also resets all
              6    0 = DSR always on.
                   1 = DSR on only if channel is available.
              7    0 = Cisco-PPP-flag-hack off.
                   1 = Cisco-PPP-flag-hack on.

       13 (default 4)
              Bit-mapped register.
              Bit  Description
              0    0 = Use delayed sending of data.
                   1 = Immediately send data.
              1    0 = T.70 protocol off.
                   1 = T.70 protocol on.
              2    0 = Don’t hangup on DTR low.
                   1 = Hangup on DTR low.
              3    0 = Standard response messages.
                   1 = Extended response messages.
              4    0 = CALLER NUMBER before every RING.
                   1 = CALLER NUMBER after first RING.
              5    0 = Disable extended T.70 protocol.
                   1 = Enable extended T.70 protocol.
              6    0 = Disable RUNG message.
                   1 = RUNG on cancelled incoming call.
              7    0 = Disable display messages from net.
                   1 = Enable disable messages from net.

       14 (default 0)
              Layer-2 protocol.
               0 = X75/LAPB with I-frames.
               1 = X75/LAPB with UI-frames.
               2 = X75/LAPB with BUI-frames.
               3 = HDLC.
               4 = TRANSPARENT.
              10 = Analog Modem. (only if hardware supports this)
              11 = Fax G3. (only if hardware supports this)

       15 (default 0)
              Layer-3 protocol.
              0 = transparent
              1 = transparent with audio features (e.g. DSP)
              2 = Fax G3

       16 (default 250)
              Outgoing packet size / 16.

       17     reserved.

       18 (default 4)
              Service-Octet-1 to accept or to be used on dial out.
              Bit-mapped register.
              Bit  Description
              0    Service 1 (audio) when set.
              1    Service 5 (BTX) when set.
              2    Service 7 (data) when set.

              Note: It is possible to set more than one bit. In this case,  on
                     outgoing  calls,  the most significant 1-bit is chosen to
                     select the outgoing service octet. On incoming calls  the
                     selected  services  are accepted, contents of register 14
                     is ignored and the Layer-2-protocol is automatically  set
                     with  the  following  values  to match the service of the
                     incoming call:

                     Incoming service audio (Reg. 20.0 = 1)
                             L2-protocol is set to 4 (TRANSPARENT).

                     Incoming service BTX (Reg. 20.1 = 1)
                             L2-protocol is set to 0 (X75/LAPB with I-frames).

                     Incoming service date (Reg. 20.2 = 1)
                             L2-protocol is set to 0 (X75/LAPB with I-frames).

       19 (default 0)
              Service-Octet-2 (ignored when using EDSS1).

       20 (read only)
              Service-Octet-1 of last incoming call. This bit-mapped  register
              is  set on incoming call (during RING). Mapping is the same like
              register 18.

       21 (read only)
              Bit-mapped register. Set on incoming call (during RING)  to  the
              value  of  octet  3  of calling party number Information Element
              (Numbering plan).  See section 4.5.10 of ITU Q.931.

       22 (read only)
              Bit-mapped register. Set on incoming call (during RING)  to  the
              value  of  octet  3a of calling party number Information Element
              (Screening info).  See section 4.5.10 of ITU Q.931.

       23 (default 0)
              Bit-mapped register.
              Bit  Description
              0    0 = Disable CPN extended RING.
                   1 = Enable CPN extended RING.
              1    0 = Disable CPN extended FCON.
                   1 = Enable CPN extended FCON.

       NOTE   There used also be cui devices (major  device  number  44),  but
              since  the  cua  devices  for  regular tty devices are no longer
              supported in the kernel, these are also no longer supported  for


       Fritz Elfert <>
       modified by Paul Slootman <>


       icnctrl(8), telesctrl(8), isdninfo(4), isdn_audio(4), isdnctrl(8).