User`s manual

U.S. Robotics I-modem Command Reference
Handshaking, Error Control, Data Compression, and Throughput • Page 11-9
instance that this may be necessary. (See Appendix A, Alphabetic Com-
mand Summary.)
Dual Standard Handshaking
We recommend that I-modems retain the default B0 and &N0 settings. This allows them
to make analog connections with
ÒV.Ó protocol
and HST modems in both Originate and Answer modes at a variety of
speeds.
When originating an analog call and the I-modem is set to B1, it sends out a Bell answer
tone, which is the prevalent standard in the United States and Canada for connections at
2400 bps and lower. At higher speeds, the I-modem also recognizes the ITU answer tones
necessary for connecting with V. protocol modems, and adjusts to the answering device.
However, when answering a call, an I-modem sending out the Bell answer tone (B1) won't
be recognized by V. protocol modems. The calling modem, instead, will wait until it
detects a tone it recognizes. The V.22bis tone used at 2400 bps.