[GreenKeys] Selectric Printer

[Christian Gauger-Cosgrove]

On 23 November 2014 at 12:39, David Burns <dvdbrns at rcn.com> wrote:
> The selectric mechanism in an ASCII  terminal was the IBM 2741 which ran at
The Selectric and related terminals (1052, 2741, and "I/O Selectric")
are NOT ASCII machines, they speak variously, a rather strange EBCDIC,
or their own special little code. In fact, actually, the not-ASCII
fact was a mild sore point for some programmers and even the engineers
who developed the original Selectric and Selectric II mechanisms. The
88-character type ball is not enough to hold the full ASCII printable
character set. The later Selectric III mechanism with its 96-character
typeballs was, however ASCII (but it was not a terminal).

Of course it could still print out RTTY, and I'm pretty sure you can
still do stuff like writing code in C using the "I don't have full
ASCII" macros.


> 134.5 baud...."Not Your Average" baud rate.  The odd baud rate means that to
> see RTTY on it, a baud-rate converter is needed.  Maybe somebody has done
> it, but a Model 15 is easier.
>
Actually, running any Selectric "outside" of its nominal baud rate
plays merry hell with the clutch. Actual "proper" Selectric terminals
were built much more robustly than the standard Selectric typewriters,
however there's a few examples floating around of normal Selectric
typewriters being used as output machines, by virtue of a box of
computer controlled solenoids hitting the keys. The latter can and
does easily kill the typewriter, as the consumer models are not
designed to print for very long periods without pause.


> Here's a YouTube video  of somebody testing a 2741.
>
That's a video of/by Mike Ross. He owns the Corestore, which I think
is one of the biggest private collections of classic computers. He
also owns an IBM System/3, and two PDP-15s.


> The computer console for Series 360 computers was the IBM 1052.
>
> The IBM "Memory Typewriter" was the Model 85.
>
Of interest, the console for the IBM 7030 "STRETCH" was also a 1052,
if I recall. But at that point that they started advertising the 7030
the Selectric hadn't come out yet so every advertising photograph
clearly had some obstruction blocking the console terminal from view.

More fun computer facts:
---> The console terminal for the DEC PDP-1? An IBM Model B modified
by Soroban Engineering
---> Early PDP-11 UNIX versions could "speak" Selectric terminal,
specifically 2741, code; also several PDP-11 serial port cards have a
134.5 baud rate setting.
---> Unlike a Model 33 or Model 35 Teletype, the Selectric terminals
were half-duplex; further the 2741 (I'm not sure of the 1052) used a
"token-passing" like arrangement for communications; one end would
send an End of Text character which would allow the opposite end to
begin sending.
---> 88-character typeball means the Selectric I, Selectric II, and
terminals like the 1052 and 2741 cannot "work" the full ASCII
character set; the 96-character typeball from the Selectric III
(released in the 1980s)
---> While the I/O of the terminal Selectrics could be pretty much
anything, the Big Box of Electronics that did the
transmission/reception, and the Selectric mechanism itself, only
"spoke" Selectric tilt/rotate options to position the typeball.
---> Apparently, the speed of the Selectric could be adjusted to
accommodate faster typists, but correspondingly this resulted in more
frequent maintenance.


> The selectric mechanism was designed for human-speed use from a keyboard,
> and the mechanism proved not as durable as would be hoped when driven from
> sources other than a keyboard.
>
Oh, I hadn't remembered when you wrote this. But yes, I agree. Though
the terminal Selectrics were built more robustly to take the "abuse"
of constant printing.


> That said, if you have a selectric mechanism, Bill Skillman can get it
> running 'just fine':  http://www.selectric.com/
>
Hmm. I wonder if he'd be able and/or willing to modify a Selectric III
as a terminal, I don't have any form of Selectric, but I could
probably get my hands on a Selectric III relatively easily. And I love
how crisp the output of a Selectric looks.



Cheers,
Christian

-- 
Christian M. Gauger-Cosgrove
STCKON08DS0
Contact information available upon request.