Multi-Tech Systems ISIHP-2U - Manual (Page 85)

MultiModemISI Hybrid Series, ISIHP-2S/2U/4S/4U/4SD 85
Modem AT Commands & S-Registers
initiating the handshake between the two modems.) At higher speeds
(2400 bps and above) there is no conflict because all protocols use the Bell
frequency of 2225 Hz. Lower speeds require different frequencies.
B0 selects ITU-T V.22 mode when the modem is at 1200 bps.
B1 selects Bell 212A when the modem is at 1200 bps. This is a default.
B15 selects V.21 when the modem is at 300 bps.
B16 selects Bell 103J when the modem is at 300 bps. This is a default.
Cn Dummy Command
-Cn Data Calling Tone
n = 0 or 1
Default: -C0
The data calling tone is a tone of a certain frequency and cadence, as
specified in the V.25 standards, which identifies whether it is remote data,
fax, or voice. The frequency is 1300 Hz, with a cadence of .5 s on and 2 s
off.
-C0 disables the V.25 data calling tone.
-C1 enables the V.25 data calling tone.
F Dummy command
&Gn Guard Tones
n = 0, 1, or 2
Default: &G0 (models outside U.K.) or &G2 (U.K.
models only)
Controls the presence or absence of guard tones from the transmitter when
in answer mode at either 1200 or 2400 bps. Guard tones are used in Europe
and other areas to allow the modem to function in the telephone systems.
Guard tones are not used in the United States. U.K. models are locked at
&G2 (1800 Hz guard tone).
&G0 disables ITU-T guard tones.
&G1 enables ITU-T 550 Hz guard tone.
&G2 enables ITU-T 1800 Hz guard tone.