What's a "computer console" selectric called?

From: Don Maslin <donm_at_cts.com>
Date: Thu May 27 17:47:06 1999

On Thu, 27 May 1999, Arlen Michaels wrote:

> 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

Didn't you also have to feed it EBCDIC instead of ASCII in order for it to
'understand' what you wanted printed?

                                                 - don

> 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 - 17:47:06 BST