Help for Zmodem

This advanced protocol is very fast and very reliable, and offers
many features. It can arguably called the most popular protocol in
use today, and should be used whenever possible. Zmodem can transfer
a group of files in one batch and keeps the exact file sizes and
dates. Zmodem can detect and recover from errors quickly, and can
resume an interrupted transfer at a later time (you may have to
confiogure your communications program to enable this feature before
resuming an interrupted download). Zmodem is also very well suited
for satellite links and packet switched networks.

Zmodem tranfers files in block sizes ranging from 128 bytes to 8k
(8192) bytes, adjusted dynamically as line conditions change.  Zmodem
does not wait for acknowledgement of a block before transmitting the
next block, and is capable of 98-99% of the theoretical maximum
transfer rate.