DTE to Modem
Modem to DTE Description and Interpretation
#CLS=8 Configure the modem for Voice Mode. (The #BDR setting
is assumed to be zero here, meaning that no time-out
occurs forcing #CLS=0.)
OK The modem agrees, and is now set up for voice.
#VBS=4 The DTE asks for 4-bit compression for greeting
message playback. The DTE needs to work at 38,400
bits/s since after start and stop bits are added, the
speed increases to 36,000 bits/s.
OK The modem is configured for 3-bit compression.
#VSD=1 This enables silence deletion.
OK The modem confirms command reception.
#VLS=0 Select the telephone line as the source, ensuring
that the modem is now on-hook. DTMF detection is now
off regardless of the previous setting of #VLS.
OK The modem confirms command reception.
#VSS=2 Set silence detection sensitivity.
OK The modem confirms command reception.
#VLS=0 Select the telephone line as the source, ensuring
that the modem is now on-hook. DTMF detection is now
off regardless of the previous setting of #VLS.
OK The modem confirms command reception, and it switches
in the telephone line.
RING Some time later, we receive the first call. (The
modem also processes Caller ID information at this
time.)
#CLS=8 Configure the modem for Voice Mode again. Although
the modem has already been so configured, it is a good
idea to select #CLS=8 directly following a RING
because in normal use, any S30 time-out or hang up
during Voice Mode forces #CLS=0.
OK The modem agrees, and is now definitely set up for
voice.
#BDR=16 The DTE knows that compression requires a 38,400
bits/s speed, so it forces this as the new speed. (For
example, lets say that the DTE was sending all
commands, including this one, at 9600 bits/s.)
OK This OK message is sent at 9600 bits/s, but the modem
then switches to 38,400 bits/s. All subsequent
commands are assumed to be sent at 38,400 bits/s until
either another #BDR command is received or until the
S30 timer expires. The S30 timer is now activated, and
the default is sixty seconds.
A The DTE tells the modem to answer.
VCON The modem is now in Online Voice Command Mode. DTMF
and calling tone detection is enabled.
#VTX The DTE does not wait for any tones, and tells the
modem that it is ready to send a voice greeting at the
current compression and sampling settings
(4-bit/7200).
CONNECT The modem tells the DTE that it can now send data.
The modem enters Voice Transmit Mode and DTMF
monitoring is still enabled as well as the ADPCM data
flow.
<Data> The DTE sends greeting message data. The modem waits
up to one second or until XOFF threshold is reached
before starting to transmit to ensure uninterrupted
data flow. If the voice transmit buffer runs empty,
the transmission is disabled.
<DLE> The DTE has finished with its transmission, and now
<ETX> instructs the modem to enter Online Voice Command Mode
since this is the telephone line.
VCON The modem tells the DTE it is done. If the DTE sends
the <DLE><ETX>before the modem has finished
transmitting all the data in its voice transmit
buffer, the DTE must wait for this response.
#VBT=12 The DTE requests that DTMF digits be sent as
"beeps"with the #VTS command while in Online
Voice Command Mode, with each beep having a duration
of 1.2 seconds.
OK The modem confirms command reception.
#VTS=# The DTE sends a beep to annotate its greeting
message. This beep is a 1.2 second long DTMF#. During
this period, the no abort is possible from DTE, and
should not be necessary.
OK After the modem sends the beep, it sends VCON to
inform the DTE that it is ready to move on. DTMF pass
through is re-enabled.
#VBS=3 The DTE asks for 3-bit compression to recorded
message. The DTE needs to work at 38,400 bits/s since
after start and stop bits are added the speed
increases to 27,000<N>bits/s.
OK The modem is configured for 3-bit compression.
#VRX The DTE instructs the modem to turn the line around
and begin recording a message from the remote.
CONNECT The modem sets things up and enables ADPCM data
transfer to the DTE with the current silence deletion
setting.
<Data> ADPCM data is shipped to the DTE with shielded DTMF
tones folded in. The modem is looking for silence,
busy, dial tone, and loop break. The DTE records
everything in its storage media.
<DLE>b The caller has finished, hung up, and in this case, a
busy cadence was detected before anything else such as
expiration of the #VSP silence detection period.
X The DTE uses a key abort to respond to a busy
detection.
<DLE> The modem is now in Online Voice Command Mode.
<ETX>
VCON
H DTE sends modem to #CLS=0 with #BDR=0.
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