USRobotics V.34 user manual Modulation, Error Control/Data Compression

COURIER HIGH SPEED MODEMS

		Modulation
Bn	Handshake options. There are three commands that apply to
	international calls above 1200 bps⎯Bn, &Gn, &Pn. See
	International Calls later in this chapter for information on the
	other two settings.
	B0	ITU-T (formerly CCITT) answer sequence. Default. This
		is required to answer all V.32-type calls, as well as calls
		from overseas.
	B1	Bell answer tone. This setting selects HST modulation in
		Dual Standard modems, but should only be used if the
		modem is not required to answer V.32-type calls.
		NOTE: This setting is required for HST cellular calls.
		Error Control/Data Compression
&Mn	Enable ARQ (error control) or synchronous protocols. Both
	your modem and the remote modem must use the same
	protocol.
	&M0	Normal mode, no error control. Due to the nature of
		phone line channels, this is never recommended for calls
		above 2400 bps.
	&M1	This setting is exclusive of the modems' error control and
		is used only for online synchronous mode without V.25
		bis. See Appendix F for more information .
	&M2	Reserved.
	&M3	Reserved.
	&M4	Normal/ARQ mode. Default. If an ARQ connection isn't
		made, the modem operates in Normal mode, as though it
		were set to &M0.
		NOTE: When V.32-type modems revert to Normal
		mode, they transfer data at high speeds without the
		reliability of error control. To avoid this, both local and
		remote modems should always be set for error control.
		Modems in HST mode, if unable to establish an error
		control connection, drop to 2400 bps.
	&M5	The modem enters ARQ asynchronous mode. The
		modem hangs up if an ARQ connection cannot be made.

Data Mode Operations 4-19