Monthly Archives: April 2014

More on the Racal-Vadic VA3451S Auto-Dial Modem

A little searching around on the Googles turned up some information I didn’t already know about my beloved modem:

  • Racal introduced the VA3451S in 1982.  It retailed for $900.
  • The modem is based on the VA3400 protocol, which was developed by Racal and introduced in 1973, nearly ten years before the ’51S hit the market.  The protocol allowed full-duplex 1200-bps transmission over two-wire connections, a thing not previously possible.
  • Bell introduced its more-capable 212A modem three years later.  The 212A is incompatible with VA3400.  Fortunately, Bill Blue and Mark Robbins thought to include multiple protocols when they developed AE Pro.
  • Wang sold a re-branded version of this modem creatively called the WA3451S for its line of workstations and terminals.

And this, I was able to pull from the musty cobwebbed corners of my brain: the init string is S0=0 E1Q0V1X4&K3.  I know this because I had to key it in every time I loaded up AE Pro to wake the modem up.  Eventually, I discovered AE Pro’s awesome macro language and I never had to type it again, but not before it was scored into the gray fleshy folds of my brain matter.

Also, there’s a manual specific to the 3451S out there somewhere (that I never got to see since ours was a second-hand modem, inherited from my father’s place of work).  The manual goes into much greater depth on my specific model.   I’d love access to a PDF copy, if anyone can point me in the right direction.  Apparently, it’s part of a TOSEC collection, but I can’t locate it.

This old modem

As I was rooting through the storage unit the other day, in search of something entirely unrelated to anything Apple II’ish, I stumbled across my very first modem.  I thought I’d disposed of this thing years ago and was happy to learn I was mistaken.  I was almost as happy to learn that I’d had the sense to make sure I packed the massive power brick along with the rest of it. I despise proprietary power connectors for this very reason.  I don’t blame developers for rolling their own but I’m terrible at keeping track of them, especially as the years begin to roll by.  The worst offenders are the companies who don’t bother to mark the brick with information about what it’s intended to couple to.  But that’s another rant…

My father originally brought this home from work when the company he worked for, NCR, bought his engineering department a handful of Apple ///’s so they could put in extra hours at home on the weekend.  My dad and a few other key personnel each got one and every Friday night, he would pack that 26 lb monster and all its accessories into the family Opal, drive it home, unpack it again and set it up in his study.  On Monday morning, back it would go.

When NCR replaced their ///’s with shiny new IBM PCs, he got to keep the modem and it integrated nicely into the family II Plus (and later, IIe).

To get back on topic, I plugged it into my IIe to see if it still worked.  Spoiler alert: it did not, so I decided to take it apart for a little quick & dirty troubleshooting.  Here are some photos and notes I took.

(Click on the thumbnails for full-size images.)


2012-07-14 10.38.32

The Racal-Vadic Auto-Dial VA3451 300 bps modem.  This little baby and me, plus my hacked up copy of ASCII Express Pro, made one lean, mean BBS-in’ machine.  The manual states that this model could also do 1200 bps out of the box, but I specifically remember that it would only do 300 for the first few years we had it.  It wasn’t until I bought a PROM upgrade that the blazing speed of 1200 characters per second was unlocked.


2012-07-14 10.39.26

Self-test instructions are clearly delineated on the bottom of the modem.  Note the lack of screws holding the unit together.


2012-07-14 10.39.58

Back of the modem, showing the switches, phone and power cables and the 25-pin serial connection.


2012-07-14 10.41.49

With the cover off, we can see that the modem is a two-board device with lots of chips.

(More after the jump.)

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