Maybe I'm just reading the man pages wrong, but...

With the following line in my /etc/ttys file:
 tty00	"/usr/libexec/uugetty std.19200"  dialup on dtrcts
After running ttyflags, stty shows that cdtrcts has been set on the line.
If I also add the mdmbuf flag though, stty causes the SD light on the
modem to stay on and the machine locks solid.  This is under 1.3 release
on an SE/30.

-- 
 mlh@csranet.com
(Michael Hendrick)