Racal-Vadic VA3451 Modem Problem

[russell at ucb-vax.ARPA]

In order to get connected to the CSNET PhoneNet, we bought a Racal-Vadic
VA3451 Auto-Dial modem.  The modem was delivered in early 1985, and the
manual that came along with it was entitled "VA3451 Modem Installation/
Operation Manual", "Initial Issue", "November, 1984".  There appears to
be an problem with the modem and an error in the manual.

After we put the modem into service, it occasionally got itself into a
funny state.  The modem was off-hook even though there was no connection,
and the modem was generating a carrier.  The lights that were lit were:
HS, DSR, and DTR.  Further, disconnecting the modem from its DTE by
removing the RS232 plug (thereby dropping DTR) did not cause the modem to
go on-hook.  Neither did unplugging the modem from the phone line.  It
was possible to force the modem to go on-hook either by toggling power or
by flipping the DA/VO/MA switch on the front panel away from VO and then
back.

I telephoned the Racal-Vadic Service Hotline, and we tried a several
months worth of different things, but nothing would make the problem go
away.

On Wednesday, 5/29/85, Diane Dustman, CSNET-CIC Technical Staff, phoned
me to tell me that our modem was off-hook.  She asked me to reset the
modem so that CSNET-RELAY could begin to call our host again.  I told
her that I knew about the problem and that I was working on it.  I asked
her if she often had to telephone site liaisons asking for a modem to be
reset.  She said that she sometimes did, but that it didn't strike her
as a widespread problem.  In any case, she mentioned my problem to Dan
Long, CSNET Technical Liaison, and it jogged his memory.  He sent on to
me something he had received in early 1984.

It was an article, signed by "--Lauren--", that had been distributed to
the INFO-MICRO, INFO-CPM, UNIX-WIZARDS, and TELECOM interest groups.
Charles Lindahl at "ti-csl" (Texas Instruments Central Research Labs in
Dallas) had forwarded the article to Dan Long.  Briefly, the article
described exactly the problem that we were experiencing with our modem.
The article said that the fix involved changing the strapping so that
the A1 switch was OFF.  The setting of the A1 switch is ignored, and A1
is considered as ON, if the modem is set to its "Standard Configuration"
via the A6 switch.  The article said that A6 should be set to ON in
order to turn off the "Standard Configuration", i.e., to enable all the
other switches.

I had set A6 to the non-"Standard Configuration" setting, but according
to my manual, that setting was achieved with A6 OFF, not ON as was
indicated in the article.  The fact that the manual I have is wrong was
verified by a Racal-Vadic Field Service representative.  I will forward
a copy of this to him, in order to be sure that the error in the manual
is corrected.

Unfortunately, I cannot tell you yet that, by setting A6 to ON and A1
to OFF, our problem has been solved.  I had mailed the modem back to
Racal-Vadic for repair just before I got the information from Dan Long.

In any case, I would like to express my thanks to Diane, Dan, Charles,
and Lauren for getting this information to me.

Michael Russell
russell at ucd.csnet
...!ucbvax!ucdavis!bluebell!russell
ucdavis!bluebell!russell at berkeley.arpa
russell%bluebell%ucdavis.uucp at berkeley.arpa