[GreenKeys] Printing Selectric

[Jim Haynes]

There were several versions of the electrified Selectric.  I remember we 
had a plain Selectric typewriter in the Teletype museum, along with a
card saying how easy it would be to adapt it to teleprinter use since
it went through a six-bit code between the keyboard and the printer.
Sadly Teletype engineers didn't seem to pay any attention to the details
of keyboard design, so we got the 32/33/37/38 keyboard with its lousy
touch on the way to the 40 and 43.

The basic Selectric typewriter was not particularly rugged, and when used 
as a teleprinter they tended to break down a lot.  So there were more 
rugged models made.  I can think of the one used as a console device in 
the System/360 line of computers, the 1130, and before that the machine 
was used as a console device on the 1410 computer and presumably others. 
There was the IBM 1050 which was a communication product where printer, 
keyboard, paper tape punch and reader and card reader were all options. 
Then there were the 2740 and 2741.  It's my understanding the 2740 was 
intended for terminal- to-terminal communication where typewriter quality 
printing was desired, and for some reason the 2741 using a different code 
was a lot more popular as a computer terminal.  The 2741 and maybe the 
2740 also had a switch on the side that would allow it to be used offline 
as an ordinary typewriter.

I was told once that IBM never released a design to production until
the field service organization had gone over it and approved it as
sufficiently easy to repair.  One glaring problem with the Selectric
is that the mechanism is belt driven from the motor, and replacing the
belt is quite an ordeal.  So apparently field service didn't catch
that one.  You often see Selectric typewriters with an extra belt
hanging on the shaft, so that the first time the belt breaks the
service guy didn't have to undertake the difficult replacement, and
could get it back into service quickly.

I had one of those Selectric I/O writers once but sold it before I
ever did anything with it.  The one I had was bought from somebody
on the Internet, and apparently had been intended for use with some
kind of aerospace industry test equipment, as it had a military style
connector instead of the one shown in the IBM repair manuals.

There were some articles in the computer hobbyist magazines early on
that told how to interface a Selectric I/O machine to your computer.
I recall it was rather an intricate process to get maximum typing
speed; if you did what was simplest to do the typing speed came out
to be rather slow.

When G.E. was in the computer biz they used Selectrics as console devices
on the 600-line of computers.  I don't remember if they were also used
on the 400 line.  I'm not sure about others.  UNIVAC used some Teletype
Model 35 printers.  Burroughs used a Model 28 printer with its vacuum
tube 220 model computer, and Model 33s as console devices on the B5500
machines.  Believe they had previously used an I/O adapted typewriter
made by somebody else, maybe Smith-Corona.  I saw the remains of an RCA
computer that had a bunch of Model 29 RO machines attached.  One of my
friends picked up a little money by buying some of those from the surplus
dealer, converting the typing units to Model 35, and selling them to
a dealer in the Los Angeles area.  This was around 1970.

Before the Selectric IBM made I/O writers from electric typebar 
typewriters.  The 1620 computer is one example.  Practically the same
machine is the Friden Flexowriter, many of which added paper tape punch
and reader.  Back in the late 1930s-1940s IBM had a system called
Radiotype which used their typewriters and communicated by radio.
Some of these were used in WW-II by the Signal Corps - IBM writes
about them as if Teletype did not exist and Radiotype was the backbone
of war communication.