jdi@psuvax.UUCP (John D. Irwin) (10/21/83)
Excuse me, but I just saw some neat 'dz.c' kernel diffs in my new uucp code
which supposedly enable something called 'line turnaround'. I'm guessing
that that means you can run one line between two computers and use uucp from
both sides, although it might not mean that at all.
And so I'm asking:
#1: Just what is line turnaround?
#2: How is it implemented, and how hard is it to do?
--
John Irwin
Pennsylvania State University
{akgua, allegra, ihnp4, burdvax}!psuvax!jdi
(814) 238-7556Little.Fleas%hi-multics@sri-unix.UUCP (10/24/83)
From: Gary Little <Little.Fleas@hi-multics> Allmost, but not quite. Think of line turn around as "one way reversible". Either party may transmit, but not at the same time. Take 2 Amateur radio operators using FM on a frequency of about 146 mhz (2 meters). When operator A is talking, his radio is locked in the transmit mode with the receiver disabled (there is either a mechanical or a solid state relay in the radio that senses the tranmitter active and either electroniclly or physically disconnects the receiver from the antenna). In order for A to listen to B, he must unkey his transmitter, which then causes his receiver to be connected to the antenna, and now he can hear the dulcit tones of B coming out of his speaker. Line turn around is the activity that must be performed to take a communcations line currently in one mode (transmit), to the other mode (receive) of operation. This may be performed by either hardware or software, depending upon the designers budget, or whether or not he hate software types. It takes time and usually is not preferred if a full duplex system is possible (transmit receive active at same time -- you can hear him while you are talking). However, you do see it used in some bi-synchronous modems.