3Com 56K manual Leveling ASL

12-4CHAPTER 12: HANDSHAKING, ERROR CONTROL, DATA COMPRESSION, AND THROUGHPUT

If the remote device has V.FC capability, the Business 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.FC capability, the Business Modem listens to the device's answer tones to identify what standard rate the remote analog device is operating at, and adjusts to that rate.

When a Business Modem answers a call, it sends out a series of answer tone signals until both devices negotiate the best connection rate.

HST We recommend that Business Modems retain the default B0 and &N0 settings. This allows them to make analog connections with "V." protocol and HST modems in both Originate and Answer modes at a variety of speeds.

When originating an analog call, the Business Modem set to B1 sends out a Bell answer tone, which is the prevalent standard in the U.S. and Canada for connections at 2400 bps and lower. At higher speeds, the Business 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, a Business 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.

If you want to have your Business Modem connect with V. protocol modems at high speeds, make sure it is set to B0 for the ITU answer tones. It will also connect with HST modems at speeds up to 16.8 Kbps.

USR V.32terbo to USR On these analog connections, Business Modems have two features that V.32terbo result in outstanding performance: Quick Connect and Adaptive Speed

Leveling (ASL).

■Quick Connect allows two Business Modems to connect in approximately 7 seconds, a far shorter time than with most devices.

■ASL (described below in Other V.Protocol Operations) is used by Business Modems operating in V.32terbo and V.32bis modes.