A specially designed cable that allows a user to connect two
computers directly
to each other via their
communications
ports (RS-232 ports). Null modems are
particularly useful with
portable computers because they enable the portable
computer to exchange data with a larger
system. Null modem cables have the Tx
(
transmit) and Rx (
Recieve) lines crossed over, thereby allowing data to be sent
from one device to the other. They are similar to a
crossover cable where it is
the CTS (
clear to send) and RTS (
ready to send) lines are crossed over.
Null-modem cables are used for serial port connections.
