258 lines
6.2 KiB
Groff
258 lines
6.2 KiB
Groff
.\" Process this file with
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.\" groff -man -Tascii isdn_audio.4 for ASCII output, or
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.\" groff -man -Tps isdn_audio.4 for PostScript output
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.\"
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.TH isdn_audio 4 "September 1999" "ISDN 4 Linux @I4LVERSION@" "Special files"
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.SH NAME
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isdn_audio \- audio extension of ttyI ISDN character devices
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.SH DESCRIPTION
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This document describes the audio related extensions of the modem
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emulation, provided by
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.IR /dev/ttyIx .
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The
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.SM ISDN
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tty devices are equipped with a modem emulation implementing a set of
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traditional and some special AT commands. This provides easy use
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together with almost all communication software that uses modem
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commands:
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.BR minicom (1),
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.BR seyon (1),
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.BR XCept (1),
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.BR uucico (8),
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.BR mgetty (8),
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.BR dip (8),
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.BR pppd (8)
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and more. When enabled during kernel configuration, the emulator
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is capable of a reduced set of commands to support audio. To use
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audio features, an
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.SM ISDN
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card with a audio-capable low-level driver is needed. Currently
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the only audio-capable drivers are the teles and HiSax driver.
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The port speed of the
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.SM ISDN
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tty devices is always 64000 bps.
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.SH AUDIO RELATED AT COMMAND SET
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This description does
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.B not
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include the standard AT command set. For a description of the standard
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AT command set, provided by the Linux
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.SM ISDN
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subsystem, see
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.BR ttyI (4).
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All commands starting with
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.B AT+
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except
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.B AT+FCLASS
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are enabled only, if audio mode is active.
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The following
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.B audio related AT commands
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are supported by
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.SM ISDN
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tty devices:
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.TP
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.B AT+FCLASS=0
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Disable audio mode (default). This command sets register
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.IR 18 " to " 4 .
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.TP
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.B AT+FCLASS=8
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Enable audio mode. This command sets register
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.IR 18 " to " 5 .
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.TP
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.B AT+FCLASS=?
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Show possible modes.
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.TP
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.B AT+FCLASS?
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Show current mode.
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.TP
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.BI AT+VNH= x
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No function, provided for compatibility only.
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.TP
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.B AT+VNH=?
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Always showing "1".
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.TP
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.B AT+VNH?
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Always showing "1".
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.TP
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.B AT+VIP
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Reset all audio parameters.
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.TP
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.BI AT+VLS= x
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Select line
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.IR x ", where " x
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is one of the following:
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.RS
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0 = No device.
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.br
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2 = Phone line.
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.RE
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.TP
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.B AT+VLS=?
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Always showing "0,2".
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.TP
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.B AT+VLS?
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Show current line.
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.TP
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.B AT+VRX
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Start audio recording. See below for more information.
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.TP
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.BI AT+VSD= x , y
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Set silence-detection parameters.
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.RS
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Possible parameters:
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.br
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.IR x " = 0 ... 31 sensitivity threshold level."
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.br
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(default 0 , deactivated)
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.br
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.IR y " = 0 ... 255 range of interval in units of 0.1 second. (default 70)"
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.RE
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.TP
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.B AT+VSD=?
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Show possible parameters.
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.TP
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.B AT+VSD?
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Show current parameters.
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.TP
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.BI AT+VSM= x
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Select audio data format to
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.IR x ", where " x " is:"
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.RS
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2 = ADPCM-2
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.br
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3 = ADPCM-3
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.br
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4 = ADPCM-4
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.br
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5 = aLAW
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.br
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6 = uLAW
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.RE
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.TP
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.B AT+VSM=?
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Show possible audio data formats.
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.TP
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.B AT+VSM?
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Show current audio data format.
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.TP
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.B AT+VTX
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Start audio playback. See below for more information.
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.SH GENERAL BEHAVIOUR
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On incoming calls, if the application responds to a
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.BR RING " by sending " ATA ,
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depending on the calling service, the emulator responds with either
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.BR CONNECT " (data call) or " VCON " (voice call)."
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When starting audio playback or recording, the emulator responds
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with
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.BR CONNECT .
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After that, the data transfer protocol described below is used.
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It is possible to initiate full duplex data transfer by issuing
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.B AT+VRX+VTX
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in a
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.B single
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command. In this case,
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.B no
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CONNECT message is sent to the application and the protocol described
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below is started immediately.
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When stopping audio playback or recording, the message returned by
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the emulator depends on how the data transfer is stopped. If the
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data transfer is stopped by a remote hangup,
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.B NO CARRIER
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is sent to the application, while stopping data transfer with one
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of the DLE sequences,
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.B VCON
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is sent. In any case, the message is preceded by the appropriate
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DLE sequence for end of audio data and/or abort respectively.
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On outgoing voice calls, the emulator responds with
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.B VCON
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upon connection setup.
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.SH AUDIO DATA FORMAT
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When recording or playing back audio data, a kind of modified bisync
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protocol is used. When recording audio data, the modem emulator is
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considered to be the
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.BR sender ,
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while the application is the
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.BR receiver .
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When playing back, this relationship is reversed: The modem emulator acts
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as
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.BR receiver ,
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while the application is the
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.BR sender .
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With the bisync protocol the character
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.B DLE
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(0x10) has a special meaning and is used like an escape character.
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It is always followed by a second character which has the following
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meanings defined:
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.TP
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.BR ETX " (0x03)"
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End of audio data. This code has to be sent by the
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.BR sender ,
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indicating end of audio data.
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.TP
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.BR DC4 " (0x14)"
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Abort sending. This code has to be sent by the
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.BR receiver ,
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when it wishes to abort receiving data. The
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.B sender
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has to reply by stop sending data and finally indicating end of audio data.
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.TP
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.BR DLE " (0x10)"
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a single byte with value 0x10 in the data stream.
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.TP
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.B 0
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Touch-tone "0" received. Valid only in direction from emulator to application.
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.TP
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.B 1
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Touch-tone "1" received. Valid only in direction from emulator to application.
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.TP
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.B 2
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Touch-tone "2" received. Valid only in direction from emulator to application.
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.TP
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.B 3
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Touch-tone "3" received. Valid only in direction from emulator to application.
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.TP
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.B 4
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Touch-tone "4" received. Valid only in direction from emulator to application.
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.TP
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.B 5
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Touch-tone "5" received. Valid only in direction from emulator to application.
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.TP
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.B 6
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Touch-tone "6" received. Valid only in direction from emulator to application.
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.TP
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.B 7
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Touch-tone "7" received. Valid only in direction from emulator to application.
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.TP
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.B 8
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Touch-tone "8" received. Valid only in direction from emulator to application.
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.TP
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.B 9
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Touch-tone "9" received. Valid only in direction from emulator to application.
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.TP
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.B #
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Touch-tone "#" received. Valid only in direction from emulator to application.
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.TP
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.B *
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Touch-tone "*" received. Valid only in direction from emulator to application.
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.TP
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.B A
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Touch-tone "A" received. Valid only in direction from emulator to application.
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.TP
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.B B
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Touch-tone "B" received. Valid only in direction from emulator to application.
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.TP
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.B C
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Touch-tone "C" received. Valid only in direction from emulator to application.
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.TP
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.B D
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Touch-tone "D" received. Valid only in direction from emulator to application.
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.SH AUTHOR
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Fritz Elfert <fritz@isdn4linux.de>
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.SH SEE ALSO
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.BR ttyI (4).
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