US Robotics COURIER - Data Rate Commands; Software Requirements

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COURIER HIGH SPEED MODEMS
pressed and turns off until it detects that compression will work
to advantage. The special &K3 setting enables the best
throughput for already-compressed files.
See
Throughput Guidelines and Data Compression in Appendix A
for
more information, including throughput to expect for dif-
ferent kinds of files.
DATA RATE COMMANDS
The &Bn and &Nn commands allow you to select variable or
fixed data rates at the DTE and link (modem-to-modem) inter-
faces.
Throughout this manual we recommend that, if your
software allows, you select a fixed rate at the DTE interface
(&Bl) so
that it can remain higher than the rate on the phone
link.
You'll
get greater throughput regardless of the call's rate on the
phone link. Just remember to also enable Transmit Data flow
control, preferably hardware (&Hl).
For the phone link we recommend variable rates (&NO). This
enables the modem to switch its link rate to match the rate of a
remote modem, no matter what the remote modem's rate is. If
the link rate is fixed, for example at 9600 bps (&N6), the modem
only connects with modems operating at that rate. Of course, if
your application requires connections with modems at only one
rate, you may wish to set the modem to a fixed link rate.
Software Requirements
Both variable and fixed rates require communications software
support. Most communications programs support variable
rates. Not all software supports fixed rates, although this
support is increasing in program updates. Check the quick-
configuration guide that came with your modem and/ or your
software documentation if your software is a later version than
the version in the quick-configuration guide.
Interface Controls 4-13