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Chapter 6 – Voice Commands
SocketModem Global MT5634SMI Developer’s Guide 62
Sample Sessions
This section provides voice mode Send/Receive handshaking examples.
Sample Rate Selection and Suggested Compression Method
Command Response
AT+VSM=? The PC inquires about the compression methods and bits-per-sample options.
The modem reports two compression methods:
1) PCM, twelve bits per sample, timing marks, sampling rates of 7200-8000 and 11025,
three levels of silence compression sensitivity, and silence clip to 0.5 seconds;
2) The same as 1 above, but without silence compression; 3) ADPCM, two bits per
sample, timing marks, sampling rate of 7200, no silence compression, and no silence clip.
128, "SIGNED PCM", 12, 40, (7200-8000, 11025), (127-129), (0-50)
129, "SIGNED PCM", 12, 0, (7200-8000, 11025), (0), (0)
132, "ADPCM/AQ", 2, 40, (7200), (0), (0)
OK
AT+VSM=128 The PC selects the first compression method with the intent of queuing the event
detection capabilities of the modem.
OK The modem agrees.
AT+VEM=? Checks the modem event detection capability for the first compression method.
"C" The modem reports Service Level C.
0A000100
0E601800
1A803840
OK
AT+VSM=132 Selects the second compression method with the intent of querying the event detection
capabilities of the modem.
OK The modem agrees.
AT+VEM=? Checks the modem event detection capability for the second compression method.
"B" The modem reports Service Level B.
0A000100
04600000
1A803040
OK
AT+VLS? The modem inquires about what analog source and destinations are available.
The modem reports that a microphone and speaker are available:
0, " ", 0A000100, 0E601800, 1A803840
1, " T", 0A000100, 0E601800, 1A803840
4, " S", 0A000100, 0E601800, 1A803840
6, " M", 0A000100, 0E601800, 1A803840
OK
AT+VSD=? The modem inquires about what end-of-voice receive silence detection capabilities are
available.
(127–129), (50–200) The modem reports that three levels of sensitivity and a time interval between 5.0 and
20.0 seconds.
Some time later, the PC wants to transmit or receive a voice message. The PC selects 1) the first compression
method at 7200 sampling rate, enable silence compression with nominal silence sensitivity, and no silence
clipping; 2) report all modem-supported event detection; 3) set end of receive silence detection at nominal
silence sensitivity setting and for 5.0 seconds:
AT+VSM=128, 7200, 128, 0; +VEM=FFFFFFFF8; +VSD=128, 50
OK The modem agrees.
AT+VSM=129, 7200, 0, 0 The PC changes its PC/modem interface rate to 38400 bps and selects a
compression method with the least sensitive setting, with the goal of playing a message
with less distortion, and at 7200 samples per second. (Assume that the PC issued a
+VSM=? command earlier.)
OK The modem agrees.