Comtrol AT Commands - Manual (Page 182)

AT Commands for CX81801/CX06833/CX81300/CX06827 Modems Reference Manual
Conexant 102184B
5-6
+VTR - Start Voice Transmission and Reception (Voice Duplex)
This command causes the modem to start the voice transmission and reception process
(Voice Duplex) without either acoustic echo cancellation or line echo cancellation. The
modem begins the Voice Duplex State by returning the CONNECT result code to the
DTE. The modem then sends <DLE> shielded voice data to the DTE, and the DTE can
send <DLE> shielded voice data to the modem. The modem will accept data from the
DTE and send data to the DTE in the format previously selected by the +VSM command,
and use the flow control method selected by the +IFC command.
The modem signals termination of the voice data stream by appending a <DLE><ETX>
command and padding out to an octet boundary if needed. The modem will issue the
<DLE><ETX> character pair (thereby ending the modem to DTE voice data flow)
followed by the OK result code, and return to the command mode after the modem has
completely transmitted the contents of its buffer.
There are two methods to leave the Voice Duplex State: the DTE sending a <DLE><^>
shielded code or the inactivity timer elapsing in the modem. The Voice Command State
is entered upon Voice Duplex State termination.
This command will function when the input and output are from/to the same I/O device,
such as local handset, line, or mic/speaker.
Syntax
+VTR
Result Codes
OK Upon command acceptance.
ERROR The modem is not connected to the line and a non-line device.