From: utzoo!decvax!cca!gwyn@Brl@sri-unix
Newsgroups: net.unix-wizards
Title: Re: VT100/VT640 ^S/^Q and EMACS
Article-I.D.: sri-unix.3139
Posted: Mon Sep  6 18:36:54 1982
Received: Wed Sep  8 01:00:16 1982

From:     Doug Gwyn 
Date:     4 Sep 82 22:50:57-EDT (Sat)
VT100s absolutely MUST have DC3/DC1 (^S/^Q) reserved for their use
in flow control.  They generate these automatically, sometimes when
you might be surprised that they have to slow down the incoming data.

There are many other terminals with this same requirement.

By the way, all Digital Engineering VT640 Retro-Graphics users should
be aware that early firmware (pre-1.4, I think) would lose count of
the DC3s and fail to send an DC1, sooner or later, thereby locking
the terminal.  A new microcode ROM fixes this glitch.