[GreenKeys] Teletype Highspeed (>100 wpm) Equipment Question

[Don Robert House]

The Type 4 was a really neat system.  I wa lucky enough to be one of two of us that went to school on the Type 4.  In class the system ran at 2000 wpm. If an error was detected the receiver would back up the tape and punch RUBOUTS over the characters.  The sender would back up the tape and resend.  We had one sender in service.  It worked just fine and we had only one case of trouble on it, which was a minor tape handling problem.   The folks at the other end had more trouble with the receivers.  Especially if the customer forgot to empty the chad bag.

Memories,
Don
K9TTY



On Sep 2, 2012, at 5:10 PM, Jim Haynes <jhhaynes at earthlink.net> wrote:

Teletype had some experimental photo tape readers, but never produced any.
Photo readers are capable of much higher speeds than anything Teletype
needed.  They were popular with computers for that reason.

There are problems with photo readers.  If you shine the light through
the holes, then you have trouble reading yellow oiled tape because the
light will shine through the tape almost as well as through the holes.
So you see black tape used with that kind of reader.  Others depended
on reflecting light through the holes with a mirror, which had some of
the same problems and also could not read Mylar aluminized tape at all
since it is mirror-shiny.  Another variety depends on diffusely reflected
light, so Mylar reflects too well.

Teletype also wanted to be able to stop the reader on a character.  That's
hard with the really fast readers.

The CX was essentially a fast version of a typical Teletype reader.
Feeler pins that are released toward the tape by a cam and actuating
contacts, then pulling the pins back down to advance the tape feed
wheel.  The final reader I'm aware of, the DX, had contact wires that
rode on the tape, making contact as they dipped into the holes.  The
feed mechanism used as escapement.  One model, for Dataspeed Type 4,
was reversible.


jhhaynes at earthlink dot net
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