3Com 56K manual Attaining Speeds Above 28.8 Kbps, Attaining 56 K Connections

12-2CHAPTER 12: HANDSHAKING, ERROR CONTROL, DATA COMPRESSION, AND THROUGHPUT

Selective Reject is an optional part of the ITU-T V.42 (LAPM) standard.

For your modem to	Command
Enable Selective Reject	ATS51.6=0 (Default)
Disable Selective Reject	ATS51.6=1

Attaining Speeds Above 28.8 Kbps

V.34 connections at 21.6, 24, and 26.4 Kbps are common. To get connections of 28.8, 31.2, and 33.6 Kbps, line quality must be pristine end-to-end. In addition, 31.2 and 33.6 Kbps connection rates are possible only when the device to which you are connecting also runs software that supports speeds above 28.8 Kbps.

Attaining 56 K Connections

When a client x2 modem connects to a server x2 modem, the path through the telephone network between the modems is subject to the following conditions for an x2 connection to be made.

A digital connection at one end. ISPs or other online services must have a digital connection to the public switched telephone network (PSTN). Most major online services have a digital connection to the PSTN.

Only one digital-to-analog conversion. There can be only one digital-to-analog conversion in the telephone network between the x2 server modem and the x2 client modem.

Controlling the V.8 Call Indicate Tone

The V.8 protocol speeds call negotiation and specifies a call indicate tone.

Providing the call indicate tone is optional. For compatibility, we ship the

Business Modem with the call indicate tone disabled.

For your modem to	Command
Enable the call indicate tone	ATS54.6=0