3Com 56K manual Capabilities, Other Protocols, Enable, Disable

V.90 Capabilities 12-3

If you enable the V.8 call indicate tone, expect to hear a sound like a fast ringing signal while the call is being connected.

V.34 If the remote device has V.34 capability, Business Modem use a line probing technique to determine the highest speed possible under current line conditions, then they complete the connection. If the remote device does not have V.34 capability, the Business Modem listens to the device's answer tones to identify the standard rate at which the remote device is operating, and then adjusts to that rate.

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

V.90 Capabilities	The Business Modem has V.90 capabilities. The Business Modem can dial into
	V.90 servers to establish speeds up to 56K downstream.
	For your modem to	Command
	Enable V.90	ATS58.5=0 (Default)
	Disable V.90	ATS58.5=1

Other Protocols

x2 x2 client modems can receive data at speeds up to 56 kbps and send data at V.34 speeds. To use x2, the client x2 modem must connect to a server x2 modem. If clients attempt to connect to ISPs that do not use x2, the client modem will negotiate the next available modulation. For example, an x2 client modem calling into an ISP that only supports V.34, the modem will only negotiate the highest v.34 connection rate. The maximum V.34 connection speed is 33.6 kbps.

Fast Class (V.FC) After trying V.34, the Business Modem tries for the fastest possible V.Fast Handshaking Class (28.8 Kbps) connection. In order to negotiate V.FC, V.8 has to be

disabled. V.FC is not part of the ITUV.8 training sequence.

If the remote device is not V.FC capable, a connection is made using the highest compatible modulation scheme (V.32 terbo, V.32 bis, and so on, down to as low as Bell 103, or 300 bps).