I'm not sure if it's the same kind of Selectric terminal, but about 20 years
ago when I was trying to find an alternative to a Teletype to connect to my
homebrew S-100 system, I acquired a used Selectric with a set of solenoids
built inside its base to activate the printing mechanism. Maybe this is the
model you remember.
IBM had to make the base deeper to accommodate the extra actuating
solenoids, so unless you placed the Selectric into a cutout or well it would
sit too high above the desk for comfortable working. You'd energize
solenoids in various zany combinations to tilt the type-ball correctly for
each character. Electrical interface was through a 50-pin rectangular AMP
connector at the rear, and I believe the solenoids needed 48 vdc. It
weighed a ton.
Actually, the biggest challenge in interfacing this thing to a computer was
to sort out how to read one particular status signal from one of the
microswitch contacts in the print mechanism, so your computer could start
sending the next character at just the right moment before the mechanical
cycle completely finished. Else your software had to pause a few
milliseconds between characters, but there was a hidden menace awaiting if
you took this easy way and just timed out for each character to finish. The
starting-and-stopping would soon wear out the clutch mechanism. With the
high duty cycle of computer printing (rather than manual typing) you would
eventually put too much strain on the mechanism and wear it out if you
didn't poll to respond to that "ready" signal. Many people don't realize
the Selectrics were *completely* mechanical. No electronics, just complex
and elegant mechanics. A nightmare :-)
I gave mine away years ago. If I recall correctly it was a "Model 735 i/o
Selectric". Maybe that name will help you track one down. I bought mine
surplus from an outfit in England back in '77, but there were companies
selling similar models in the USA too. They ran magazine ads in the early
years of Byte and Kilobaud. There were some articles in Radio-Electronics
(of Mark-8 computer project fame) describing a Selectric interface.
Arlen
> -----Original Message-----
> From: Gary Oliver [SMTP:go_at_ao.com]
> Sent: Monday, May 24, 1999 4:35 PM
> To: Discussion re-collecting of classic computers
> Subject: What's a "computer console" selectric called?
>
> Back in the days before "glass" consoles, computers often (if
> they had them) used typewriter devices as console input and
> output stations. Many minicomputers used Teletypes, but Control
> Data used (believe it or not) IBM Selectric typewriters.
>
<snip>
--
Arlen Michaels amichael_at_nortelnetworks.com
Received on Thu May 27 1999 - 08:02:24 BST