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Chapter 3 – Voice Commands
Multi-Tech Systems, Inc. AT Commands Reference Guide (S000273F) 34
Command: +VRN Ringback Never Appeared Timer
Description: This command sets the length of time the modem will wait between ringbacks during call
origination before the modem can assume that the remote station has gone off-hook.
Syntax: +VRN=<interval>
Values: <interval> Decimal number specifying the time period, in units of 1.0 second, that the
modem will wait for Ringback during call origination.
A value of 0 forces the modem to report the OK result code immediately
after dialing.
The range is 1 to 25 seconds for <interval> = 1 to 25.
Default: Interval of 10 (10 seconds)
Result Codes: OK <interval> = 0-25
ERROR Otherwise, or if not in Voice Mode.
Report Commands: +VRN? Reports current of selected values.
+VRN=? Reports supported range of parameter values.
Command: +VSD Silence Detection (Quiet and Silence)
Description: This command causes the modem to set the silence detection sensitivity and the required
period of silence before the modem reports silence detected at the end of a voice receive
either with the “Presumed End of Message” (QUIT) or “Presumed Hangup (SILENCE)
event reports.
Syntax: +VSD=<sds>,<sdi>
Values: <sds> Decimal number corresponding to the selected parameter.
0 Use +VSM silence compression setting and algorithm for long-term
silence detection (if +VSM is in use) or proprietary silence
compression setting and algorithm for long-term silence detection (if
+VSM is not in use).
127 Sets less aggressive long-term silence detection independent of
presence or use of silence compression.
128 Sets nominal long-term silence detection independent of presence or
use of silence compression.
129 Sets more aggressive long-term silence detection independent of
presence or use of silence compression.
<sdi> Decimal number specifying the required period of silence, in units of 0.1
second, before the modem can report silence detected at the end of a voice
receive either with the “Presumed End of Message” (QUIT) or “Presumed
Hang up (SILENCE) event reports.
A value of 0 disables the modem silence detection.
The range is 0.1 to 25.5 seconds for <sdi> = 1 to 255.
Defaults: 0,50
Report Commands: +VSD? Reports current of selected values.
+VSD=? Reports supported range of parameter values.
Command: +VSM Compression Method Selection
Description: This command causes the modem to set the voice compression method, the silence
compression sensitivity, and the voice sampling rate.
Syntax: +VSM=<cml><vsr><sds><sel>
Values: <cml> Decimal number identifying the compression method.
<vsr> <range of values> containing the supported range of voice samples per
second of the analog signal.
<sds> <range of values> containing the supported range of sensitivity settings for
voice receives.
<sel> <range of values> containing the supported range of expansion values for
voice transmits.
Defaults: 1,8000,0,0
Report Commands: +VSM? Reports current of selected values.
+VSM=? Reports supported range of parameter values.