MITS Teletype Interface Board

From: Brent Hilpert <>
Date: Sun Aug 8 17:24:54 2004

I was shuffling through some papers last night and stopped for a moment to read the two copies of "Altair Notes" from
1975/76 in my possession. (Altair Notes was a newsletter for Altair owners. They're rather amusing as they have articles
written by Bill Gates and Paul Allen from the period when (if I have it correctly) they were working for MITS.)

(Also ran across an article I cut out of Technology Illustrated (Sep 1983) years ago about the inception of the Boston Computer Museum. I sure hope they weren't butchering their artifacts to add the christmas tree lights mentioned in another thread.)

In one of these Altair Notes is a small blurb and picture of a new product from MITS. For what it is worth (which isn't
much, considering how little it says about what the board actually does) below is the text. The picture matches your (Brian's) picture, but the mentioned "parts layout" is not present.

I'll speculate the "$500.00 savings" mentioned is in relation to a more expensive option from Teletype providing the
equivalent/desired functionality.

(excerpt from Altair Notes / March 1976):

New Products

Teletype Call-Control Kit

  The MITS Teletype Call-Control Kit provides a much lower cost and faster way to get a teletype into your system than was
previously possible. MITS has made an agreement with Teletype whereby the fully assembled mechanical portion of the Teletype
will be shipped directly to you from Teletype Corp. and the PC board Call-Control Kit will be shipped from MITS. Starting in
May, delivery time should be a couple of weeks as opposed to 4 to 5 months.

  There are three Call-Control Kits available: 88-TYR which is supplied with the Teletype printer only, 88-TYK which is
supplied with Teletype Model KSR-33 (printer and keyboard), and 88-TYA which is supplied with Teletype Model ASR-33
(printer, keyboard, paper tape punch and reader). All three kits use the same basic printed circuit board (see parts layout,
this page). All you need to do is assemble as much of the PC board as applies to the model of Teletype you have purchased,
mount it to the Teletype chassis, and plug it in.

  The PC board for the 88-TYR (printer) kit has a power switch, two fuses, a simple power supply and the receive circuit for
20mA current loop. Interconnect plugs and mounting hardware are also provided.

  For the 88-TYK kit, a relay for line-local switching, a connector to the keyboard, and some transient damping circuitry
are added.

  For the 88-TYA kit, all of the above is included with the addition of another simple power supply, connections for the
paper tape reader, and a circuit to control the reader by program control.

  That's all there is to it. The most complicated part of the assembly is connecting wires from the line-local relay to the
PC-board. The 88-TYA kit should take only 3 to 5 hours to complete. At $500.00 savings, that's $100.00 an hour for your


Brian Knittel wrote:
> Hi,
> For those of you who asked to see the MITS
> Teletype Interface board I mentioned a couple
> of days ago, I've put a picture at
> The molex connector at the bottom left below the relay
> is where the data cable connects. The other end is
> a DB25 connector, and the wires go to pins 2-6. Since
> there is no connection to pin 7 (signal ground) it must
> be current loop.
> Brian
Received on Sun Aug 08 2004 - 17:24:54 BST

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