User`s manual

U.S. Robotics I-modem Command Reference
Handshaking, Error Control, Data Compression, and Throughput • Page 11-6
the highest compatible modulation scheme (V.FC, V.32terbo, V.32bis, and so on, down to
as low as Bell 103, or 300 bps).
If the remote analog device has V.34 capability, the I-modem uses a line-probing technique
to determine the highest speed possible under current line conditions, then completes the
connection. If the remote analog device does not have V.34 capability, the I-modem listens
to the deviceÕs answer tones to identify the standard rate at which the remote analog device
is operating, and then adjusts to that rate.
When the I-modem answers a call from an analog device, the I-modem sends out a series
of answer tone signals until both devices negotiate the best connection rate.
Fast Class (V.FC) Handshaking
After trying V.34, the I-modem tries for the fastest possible V.Fast Class (28.8 Kbps) con-
nection. The V.FC range spans 28.8, 26.4, 24, 21.6, 19.2, 16.8, and 14.4 Kbps. If the
remote device is not V.FC- capable, a connection is made using the highest compatible
modulation scheme (V.32terbo, V.32bis, and so on, down to as low as Bell 103, or 300
bps).
If the remote device has V.FC capability, the I-modem uses a line-probing technique to
determine the highest speed possible under current line conditions, then completes the