US Robotics COURIER - Throughput Optimization Guidelines

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COURIER HIGH SPEED MODEMS
data flow changes. Interactive applications appear faster under
V.32 modulation, while connection times are faster under HST
modulation.
WARNING: To connect above 9600 bps, the DTE rate must be
19.2K, 38.4K or 57.6K bps. If the local computer is limited to
9600
bps, V.32 bis modems are limited to 9600 bps maximum,
that is V.32. Disable V.32 bis modulation so that the modem
does not switch its DTE rate up higher than 9600 bps. Do this by
setting Register S34 to 3 (S34=3) and including that setting in the
defaults you write to nonvolatile memory, as shown in the next
chapter.
MODULATION AT 2400 BPS ANO BELOW
The Bn setting is not significant at speeds of 2400 bps and lower
except for answering calls from overseas. (See International Calls
at the end of Chapter 6.) The only difference you might notice is
that the B1 setting (Bell answer tone) allows the modems to
connect slightly faster.
Error control, DTE rates, flow control
and other settings are the same for both HST and V.32 bis
modems.
THROUGHPUT GUIDELINES
The following guidelines should help you to make the most of
your modem's advanced performance features. In many
instances, experimentation and experience will indicate what
works best for your applications.
You'll
obtain optimal throughput under the following
conditions.
1. Your communications software supports a fixed DTE rate
higher than the link rate, for example, setting your software
to 57.6K, 38.4K or 19.2K bps and setting the modem to &B1.
Check the quick-configuration guide that came with the
modem or your software manual, and see Data Rate
Commands
in this chapter.
2. The call is under data compression. See Data Compression
(&Kn) in this chapter.
Interface Controls 4-3