Multi-Tech Systems MT5634SMI V.92, MT5634SMI V.34 manual Start Voice Transmission Process, 110

		Chapter 4 – Voice Commands
Command:	+VTX	Start Voice Transmission Process
Result Codes:	OK on completion of transmission; CONNECT if the modem accepts the command;
	ERROR if the modem is not connected to at least one off-hook Telco line, or one non-
	Telco device.
Description:	The +VTX command causes the modem to start the voice transmission process. The PC
	sends the data in the format of the previously entered +VSM command, using the flow
	control method selected by the +FLO command. The voice data is buffered to withstand
	gaps of missing data from the PC. If the modem does not have any current voice data,
	the modem sends silence over to the analog destination until the PC provides more voice
	data. The modem returns the OK result code and returns to Command mode after the
	modem has completely transmitted its buffer contents. The Inactivity Timer can be used
	to terminate the transmit data state, after which the modem returns to Command mode.
Command:	+VGR=<gain>	Set the Gain for Received Voice Samples
Values:	0–255
Result Codes:	OK if the modem accepts the command; ERROR if the parameter is out of range.
Description:	The +VGR= command causes the modem to set the gain for the received voice samples.
	Receive gain values larger than 128 indicate a larger gain than nominal, and values
	smaller than 128 indicate a gain smaller than nominal. The modem may limit the receive
	gain to a narrower range, such as from 120 to 136, or from 120 to 128. The value 0 is
	reserved for modem automatic gain control (AGC).
Command:	+VGT=<level>	Set the Volume for Transmitted Voice Samples
Result Codes:	OK if the modem accepts the command; ERROR if the parameter is out of range.
Description:	The +VGT= command causes the modem to set the volume control, either by attenuating
	or amplifying the signal, for the transmitted voice samples. Values larger than 128
	indicate a larger gain than nominal, and values smaller than 128 indicate a gain smaller
	than nominal. The modem may limit the receive gain to a narrower range, such as from
	120 to 136, or from 120 to 128. The value 0 is reserved for modem automatic volume
	control (AVC).
	Note: The modem will limit the transmit level over the Telco lines, regardless of the
	current +VGT setting, to that permitted by CFR FCC Rules Part 68 – Subpart D.
Command:	+VIT=<timer>	Set DTE/DCE Inactivity Timer
Result Codes:	OK if the modem accepts the command; ERROR if the parameter is out of range.
Description:	The +VIT command sets the modem's initial value for the PC/Modem Inactivity Timer.
	The permitted range is displayed by the +VIT=? command. The units are in 1.0 seconds.
	The PC can disable the Inactivity Timer by using a value of 0 (+VIT=0).

The Inactivity Timer serves to ensure that the PC does not leave the modem in a state where it is not accessible by voice-unaware software. The Inactivity Timer is activated when the PC selects the voice fixed-rate. The timer expires if the flow of data from the PC to the modem stops (in both Voice Command mode and Data mode) for a specified amount of time.

When this timer expires, the modem switches to Data mode with autobauding. By switching to autobauding (and Data mode), the PC is allowed voice-unaware software to recover control of the modem in the event of catastrophic failure that does not result in a modem power down. It is recommended that the PC software leave the modem in autobauding (and Data mode), and use the Inactivity Timer only as needed. Leaving the modem in autobauding is an extra measure to prevent confusion from voice-unaware software accessing the modem in Voice mode at a fixed PC/modem interface rate. You can use the H command to switch to autobauding and Data mode automatically. In Voice mode, the modem does not allow the auto answer feature, since this feature does not allow the PC to set the modem in Voice mode before answering the phone.

Multi-Tech Systems, Inc. SocketModem MT5634SMIxx Reference Guide (S000263C) 110