Chapter 10 - Voice Mode Operation
10-16
This command causes the DCE to start the voice transmission process. The DCE
begins the Voice Transmission Mode by returning the CONNECT result code to
the DTE. After this report, the DCE accepts <DLE> shielded voice data from the
DTE. The DTE shall send the data in the format previously selected by the +VSM
command and use the flow control method selected by the +FLO command.
There are two ways to leave the Voice Transmission State:
1. The DTE sends a <DLE><ETX> shielded code.
2. A DTE/DCE Inactivity Timer time-out.
Item (1) is the DTE initiated means of terminating the Voice Transmission State,
and item (2) is a DCE-initiated means of terminating the Voice Transmission
State. Upon termination of the Voice Transmission State, the DCE sends the OK
result code and returns to Voice Command State.
Voice Mode Configuration Commands
 AT+VGR=<gain>
This command causes the DCE to set the gain for the received voice samples. The
gain is an unsigned octet value. The normal value is 128. A value larger than 128
indicates a larger gain than normal, and a value smaller than 128 indicates a gain
smaller than normal. A gain value of 56 corresponds to -18 dB gain, 128 for 0 dB,
and 200 for 18 dB, in 0.25 dB steps. A value of zero invokes Automatic Gain
Control on the DCE. The gain range is 56 to 200 and the default value is 0.
The DCE returns the result code OK if DCE accepts this command, or it returns
the result code ERROR if the <gain> parameter is out of range.
 AT+VGR?
The DCE will return current gain, followed by the OK result code.
 AT+VGR=?
The DCE will return all permitted values for the gain. The response is:
56-200
OK
 AT+VGT=<level>
This command causes the DCE to set the volume level, either by amplifying or
attenuating the signal, for the transmitted voice samples. The transmission gain (or
attenuation) is an unsigned octet value. The default value is 128. A value larger
than 128 indicates a larger gain than normal, and a value smaller than 128
indicates a gain smaller than normal. The level range is 56 to 200. A gain value of
56 corresponds to -18 dB gain, 128 for 0 dB, and 200 for 18 dB, in 0.25 dB steps.