RS232 Cable extending

[Robin Hewitt]

There are two kinds of handshaking with IBM RS232, hard wire and Xon Xoff.

Xon Xoff are ASCII characters, basically sending an Xoff is the equivalent of, "Shut up" and Xon means "Resume transmission".

Wire involves 2 wires, One end could raise RTS, Request To Send, then wait until the other raises CTS, Clear to send, before sending the data. Data Terminal Ready, Data Set Ready are similar. Ring Indicator is to say someone is trying to dial your Modem.

Wired handshaking is uncommon, but very often people wire CTS back in to RTS and DTR back in to everyone else for instant gratification.

Back in the day the notion was that a fancy screened RS232 cable was good for 10 feet while twisted pair was good for 100 yards.