User's Manual

&G – Guard Tone
This command controls whether the modem sends out guard tones while
connected to a remote modem (for ITU-T V.22 bis {1200 bps} and V.22 bis
{2400 bps} connections only). Guard tones are sent by the answer modem to
disable Central Office echo cancelers.
AT&G0 Guard tone disabled (factory setting)
AT&G1 550 Hz guard tone enabled
AT&G2 1800 Hz guard tone enabled
&K – Select Serial Port Flow Control
This command specifies the DTE-to-modem flow control. Software flow control
uses the characters XOFF (13h) and XON (11h) to stop and start data
transmission, respectively, both to and from the DTE. Bi-directional hardware
flow control uses RTS/CTS to stop and start data from the modem
AT&K0 Disables flow control
AT&K3 Bi-directional hardware flow control - RTS/CTS
AT&K4 XON/XOFF software flow control
&S – DSR (Data Set Ready)
This command controls how the modem treats the DSR signal.
&S0 DSR circuit always on
&S1 DSR circuit is on during handshaking, off in test or idle modes. DSR
is off when the carrier is lost.
&T – Data Mode Self-Test Command
This command is used in data mode to initiate and terminate loopback tests for
testing modem-to-modem and DTE-to-modem data communication integrity.
AT&T0 Terminate test in progress
AT&T1 Local analog loopback.
AT&T4 Grants RDL request from remote modem
AT&T5 Denies RDL request from remote modem
AT&T6 Remote digital loopback
AT&T7 Remote digital loopback with self-test
AT&T8 Local analog loopback with self-test
=> You can use the Test Timer (Register 18) to end a test loop;
alternatively, once you have entered the Esc sequence (+++), you can enter
the command AT&T0.
AT COMMANDS: DATA MODEM 2-11