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COURIER HIGH SPEED MODEMS
Data Mode Operations 4-19
Modulation
Bn Handshake options. There are three commands that apply to
international calls above 1200 bpsBn, &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.