User's Manual

4.0 General Operation and Special Features

Changing the Operating Mode Fallback parameter to 1 has the following

effects:

• The Modem is configured for V.22 bis 2400 bps/V.22 1200 and 600

bps/V.21 300 bps/V.23 1200/75 bps fallback operation. As a result,

600 and 1200/75 bps appear as additional selections on the SPEED

LIMIT LCD screens.

• Fallback to V.22 bis Bell 212A and Bell 103 compatibility is disabled.

• An AT command is available (in Hayes mode only) that allows control

over operating mode as follows: F0—Multi-mode operation (default);

F1—V.21, 300 bps; F2—V.22, 600 bps; F3—V.23, 1200/75 bps; F4—V.22,

1200 bps; F5—V.22 bis, 2400 bps; F6—V.32 (highest common speed).

Except for multi-mode operation, the mode and speed are limited to the

mode and speed specified. Multi-mode operation allows the modem to

automatically fall back to the most efficient mode that can be used by

both modems.

The preferred mode is V.32 (9600 or 4800 bps, asynchronous/ synchronous,

full duplex); however, if the other modem does not support the V.32

standard, the Modem falls back to one of the modes listed below. The fallback

modes are listed in the order in which they are attempted by the Modem in

normal operation.

Table 4-5. V.22 bis/BELL 212A/BELL 103 FALLBACK (DEFAULT).

MODE DESCRIPTION

V.22 bis 2400 bps asynchronous/synchronous

Bell 212A 1200 bps asynchronous/synchronous

Bell 103 0-300 bps asynchronous

All modes are full duplex.

If V.22 bis/V.22/V.21/V.23 fallback operation is enabled, the following

fallback modes are available. As in the previous list, the modes are listed

in the order in which they are attempted by the Modem.