On Feb 21, 2022, at 6:07 PM, Guy Fedorkow <fedorkow
at mit.edu> wrote:
Yes, I should have said -- I'm looking for a machine that can punch under control
of a computer.
Whirlwind actually used seven-bit Flexowriters for reading and punching (along with a
high-speed reader later on), but I think it would be even harder to find fresh seven-level
tape even if a seven bit machine turned up.
I actually have been using a BRPE on loan from another contributor to this list, but
it's time to return the unit, so I've started to look for alternatives.
I assume something like an ASR-33 would do the trick, although a machine without
keyboard and printer might have fewer moving parts to go wrong. But I don't see many
plausible choices on ebay.
If anyone can suggest other sources, I'll poke around
The nice thing about an ASR33 (or other hardcopy terminal with reader/punch like a TT
model 15) is that you can interface them to a computer rather easily, just hook up a UART
with appropriate driver/receiver circuitry. RS232 to 20 mA (or 60mA for a Model 15)
isn't totally trivial but it certainly is no big deal. And those slow machines
actually have the nice benefit that it's easy for people to see the action, and to get
some understanding at a gut level of how slow computers were in those days.
I understand there is a group called "Green keys" -- ham radio operators who use
old "teletype" machines -- which in that community means wny sort of keyboard
telex-type machine, not necessarily made by Teletype Co. though US ones often are. 5 bit
machines are common in that crowd, some 8 bit machines also appear. I haven't
participated, but I would think that you might find pointers to options there.
As for 7 bit tape media: I found out in the past year or so that there actually was such a
thing as paper tape of width designed for 7 tracks, but a lot of "7 bit" paper
tape work actually used 1 inch wide tape, i.e., what is normally considered 8 bit tape.
For example, the Flexowriters on which I did my first programming at TU Eindhoven used a
7-bit code but on 8 bit tape.