User`s manual

U.S. Robotics I-modem Command Reference
Handshaking, Error Control, Data Compression, and Throughput • Page 11-16
Possible dictionary sizes:
I-modems use an 11-bit, or 2048-entry dictionary, but they can reduce its size to accom-
modate a remote modem that uses a 9- or 10-bit dic-tionary.
¥ Maximum string length of each entry. As the dic-tionary Þlls, the I-modem deletes the
oldest unused strings.
V.42bis compression is more efÞcient than MNP5 com-pression, in part because it dynam-
ically deletes entries that are no longer used. In addition, it works better with Þles that are
already compressed. These include .ZIP Þles and 8-bit binary Þles, which seem to
I-modems to be compressed.
MNP5 compression should not be used with such Þles because it adds data to the Þles,
which lessens throughput. (The additional data is stripped when the Þle is decom-pressed
by the remote modem.) When transfer-ring such Þles, it's best to set the I-modem to &K3.
Bits Entries
9 512
10 1024
11 2048