[GreenKeys] [External] Re: Looking for an ASR-33 Teletype

[Jones, Douglas W]

From: Harold Hallikainen via GreenKeys [greenkeys at mailman.qth.net] -- Sunday, January 30, 2022 6:43 PM

> On Sun, January 30, 2022 4:56 pm, Hill Haven Telco wrote:
>> Im looking for an ASR-33 Teletype,  I have an altair replica kit ...

> Good luck! A friend had the Altair when it first came out.

When I was a grad student at the U of Illinois at Urbana back in the 1970s, we bought Altair 8800 serial number 34 (in kit form) and built it.  Not too many months later, we also bought an IMSAI kit.  We put the Altair to good use as a 4-channel protocol converter, taking ASCII (asynch 8 bits plus parity) at 9600 baud on one side and converting it to the unique parallel format used by Magnavox PLATO IV terminals on the other side -- 21 bit parallel data, 60 packets per second, where each packet held 18 data bits (3 6-bit characters or 2 9-bit coordinates) plus 3 "opcode" bits and a parity bit.

It was a hoot writing the software to do that job in 8080 assembly language, not to mention building the custom S100 interface boards for the 21-bit parallel interface to the PLATO terminals.  We never used any teletypes in that lab.  All our ASCII terminals were what people called "glass teletypes" (dumb terminals like ADM31s), and we standardized on 9600 baud.

We did all of our software development for the Altair on our Modcomp IV minicomputer, no paper tape involved.

I should note, with strong feelings, that the IMSAI was a immensely better built S100 machine than the Altair.  Our IMSAI ended up running a mouse experiment in the med school -- with a digital scale, microphone, and speech recognition software.  They had thousands of mice that each needed to be weighed daily, so the lab tech would pull out a mouse, put it on the scale (in a beaker), read the serial number of the mouse, say mark to indicate when to weigh, then put that mouse back and get the next one.  This was, admittedly, early speech recognition, but it worked and allowed the techs to pay attention to the mice, not the pens and clipboards that used to take up half their time.  A horrible job made just a little less horrible by adding a computer.  I left in 1980, so I have no idea what happened to that stuff after that.

           Doug Jones
           jones at cs.uiowa.edu