Operating Mode

The Fax/Data Modem operating modes, which is selectable by the \Nn command, these commands allow the DCE (modem) to communicate with remote modems that may or may not support error correction and data compression. The operating modes are Normal, Direct, Reliable link, Auto-reliable, V.42 Reliable Mode, and MNP Reliable Mode. Speed buffering, which is used for all operating modes except \N1, allows the DTE(computer)-to-modem data rate to be different from the modem-to-modem data rate. This is accomplished by using transmitting and receiving buffers in the modem as speed buffer. Thus, the DTE-to-modem data rate can be set for 38,400 bps when the modem-to-modem data rate is 9,600 bps, without causing any data errors. In all data modes except direct mode (\N1), the DTE-to- modem data rate can be set for any valid speed between 300 bps and 57,600 bps. (In direct mode, the DTE-to-modem data rate can only be set to 300, 1200, 2400, 4800, 7200, 9600, 12000, and 14400 bps.)

Each operating mode is explained as the following:

Normal Mode	%	No error correction/data compression, but speed
		buffering is supported.
Direct Mode	%	No error correction/data compression and speed buffering.
Reliable Mode	%	V.42, V.42 bis or MNP 2-5 only connection. The modem hangs up if a V.42/V.42 bis/MNP 2-5
		connection cannot be established.
Auto-Reliable Mode	%	V.42/V.42 bis with fall back to MNP 2-5 or normal mode.
V.42 Reliable Mode	-	V.42/V.42 bis connection only. The modem hangs up if an V.42/V.42 bis connection cannot be established.
MNP Reliable Mode	%	MNP 2-5 connection only. The modem hangs up if an MNP connection cannot be established.

If you have difficulty connecting to a remote modem, try using the Normal mode or Direct mode.

The table below shows the \Nn and other commands needed to setup a desired operating mode.

Operating Mode

Data/Fax Modem Speed

All of these commands have a prefix AT&F

2400

9600

14.4/14.4

14.4/14.4CL

28.8/14. 4

- 14 -