[Fwd: Re: Altair 8800] - test-drb@ccmp.vtda.org

29 Sep 1997

...
 From: Eric Chomko &lt;chomko(a)IDT.NET&gt;
Newsgroups: alt.folklore.computers
Subject: Re: Altair 8800
Date: 19 Sep 1997 03:47:25 GMT

Tim Shoppa &lt;shoppa(a)alph02.triumf.ca&gt; wrote:
: In article &lt;341776C1.426ED8F0(a)odyssee.net&gt;et>, DAN  &lt;dlessard(a)odyssee.net&gt;
wrote:
...
 : >Once someone loaded the Micro-Soft Basic into the
Altair via switches,
: >paper tape or disk, how did they enter the program? Also through paper
: >tape or did they have a keyboard to write a simple program?

: Typically they had a Teletype or some other sort of terminal to
: run Basic on.  Often, the paper tape reader was part of the teletype.

TTYs and Altair did not mix. Their 20 milliamp current loop interface was
for shit if I remember correctly. If theyever had one. Can an Altair owner
with a TTY make me a liar? 
Um, yes. (having a few Altairs and TTYs which I still run)  The Altair
(MITS) serial cards and 20mil TTYs got along just fine, once you resolved
one minor issue.

The 20mil drivers on the MITS cards were fine, with the exception that they
*did not source the receive (keyboard) loop* !

This was not properly documented anywhere, and caused many a person endless
grief trying to get it to run...

It would appear that MITS was not the first to approach the issue in this
manner (so who knew just what voltage you needed to run???  considering
line length and all) since the problem was easily (once you knew the
secret) resolved by installing one jumper *in the TTY* which existed for
just such a purpose (and was documented in the Teletype manuals).

-jim

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