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4 AT Commands, S-Registers, and Result Codes
39
Command: &G
n
V.22bis Guard Tone Control
Values: n = 0, 1, or 2
Default: 0 (North America), 2 (elsewhere)
Description: &G0 Disables guard tone.
&G1 Sets guard tone to 550 Hz.
&G2 Sets guard tone to 1800 Hz.
Note: The &G command is not used in North America, and
may not be permitted in some countries.
Command: &K
n
Flow Control Selection
Values: n = 0, 3, 4, 5, or 6
Defaults: 3 (data modem mode)
6 (fax modem and voice modes)
Description: &K0 Disables flow control.
&K3 Enables CTS/RTS hardware flow control.
&K4 Enables XON/XOFF software flow control.
&K5 Enables transparent XON/XOFF flow control.
&K6 Enables both RTS/CTS and XON/XOFF flow control.
Note: See also the &E command
Command: &M
n
Communications Mode
Values: n = 0–3
Default: 0
Description: This command determines the DTR operating mode. The mo-
dem treats the &M command as a subset of the &Q command.
&M0 Selects direct asynchronous operation. Note that the command
sequence &M0\N0 selects normal buffered mode, but the
command sequence \N0&M0 selects direct mode. This is be-
cause the \N0 command is analogous to the &Q6 command.
&M1 Selects synchronous connect mode with asynchronous offline
command mode.
&M2 Selects synchronous connect mode with asynchronous offline
command mode. Same as &M1 except that &M2 enables DTR
dialing of directory slot 3. The modem disconnects if DTR is
low for more than the period stored in S25.
&M3 Selects synchronous connect mode. This mode allows DTR to
act as a talk/data switch. The call is manually initiated while
DTR is inactive. When DTR becomes active, the handshake
proceeds in originate or answer mode according to S14 bit 7.