🚀 go-pugleaf

I need some help in a big way here.  All I want to do is set up some
modems so users can dial in to our MicroVax-II.  We're running Micro-VMS
and have a 16 port Emulex multiplexer board.  It took the phone company
5 tries before we had our phone lines working (but that's another
story).  The first problem seems to be the modems.  Has anyone ever used
Codex 2233's?  These are 2400 baud modems with about 59 million
different options.  Unfortunately, the options seem to have a habit of
changing value by themselves seemingly at random.

Specific problems include at various times randomly getting wedged such
that only cycling power will reset them; failing to answer the phone
even though set to autoanswer mode; going off-hook when no one is
calling; answering the phone and then rudely hanging up on the caller;
going into analog-loopback; and getting stuck at 300 baud (not resetting
to 2400 for the next caller).  On dialout, they lock up if they call a
host running at 1200 baud (they drop down from 2400 to 1200 OK, but then
refuse to send any data).  After several days of floundering, we decided
we didn't really want non-deterministic modems.  We then tried a BytCom
modem.  This had the unfortunate property of not releasing the line when
the caller hung up (yes the port is set to "hang").  Next we tried a
"Mikon" modem (don't ask me where they come from - I just install them).
This seems to work OK sometimes, although it also sometimes hangs up
immediately after answering.

Anyway, my questions are: what kind of modems do you use on your Vax for
dial-in's?  What lines does the Vax use to control them?  (We're using
DSR, CD, and DTR).  I've noticed that our Vax normally holds DTR (pin
20) high on idle modem ports, but occasionally cycles it low for about a
second, then brings it high again.  Why does it do that?  Could that
explain the hang-up problem (like if someone is unfortunate enough to
call in just when the Vax drops DTR, that would make the modem hang up)?
Any and all help would be most appreciated.

			- Michel
			Denber.wbst@Xerox.COM