User`s manual

U.S. Robotics I-modem Command Reference
Dialing, Answering, and Hanging Up • Page 3-8
B0 ITU-T (formerly CCITT) answer sequence. Default. This is required to
answer all V.34-type calls, as well as calls from overseas.
B1 Bell answer tone. This setting selects HST modulation, but should only be
used if an I-modem is not required to answer V.34-type calls.
&Gn This setting applies only to analog overseas calls at 2400 or 1200 bps. British
phone switching systems require devices to send an 1800 Hz guard tone after they
send an answer tone. Some other European phone networks require a 550 Hz guard
tone. Guard tones are not used in the United States or Canada.
&G0 No guard tone. This is used in the United States and Canada. Default.
&G1 This sets a 550-Hz guard tone, which is required in some European coun-
tries.
&G2 This sets an 1800-Hz guard tone, which is required in the U.K. and some
Commonwealth countries. &G2 requires the B0 setting.