[GreenKeys] Teletype Monopulse printer

[Duncan M. Brown]

> [Original Message]
> From: John Nagle <nagle at animats.com>
> To: <greenkeys at mailman.qth.net>
> Date: 20-Nov-09 12:45:52
> Subject: Re: [GreenKeys] Teletype Monopulse printer
>
>
> The early printing telegraphs had trouble staying in sync, but for the
> Teletype 36, they seem to have assumed that both ends were running from
> the same synchronous AC line, so the sync problem wasn't too hard.
>

I don't think synchronization was a big problem with the M36, since it was
such a simple system.  If TX & RX were always in the same "rest" position
at the start of a letter, then no other synchronization would be needed.  

Contrary to what I said before, the signalling pulse was a NO current
condition. Here is a description I found from the transcript of a slide
show of the original Teletype Corp. Museum.  (Someone on Greenkeys
supposedly has the orignal slides and is going to put them onto a DVD????)

-----------------------
[from "History of Telegraphy from the Teletype Museum"; Ransom D. Slayton,
Consultant;1983]



"203. There was always the push to develop lower cost units for simpler
systems. One such system was the Model 36 Monopulse.

"204. This operated much like some early stock tickers, with the line
signal being an OPEN interval during which sending and receiving devices
rotated until the proper point was reached for printing the desired
character. the Keyboard, at the left here, had its Keys mounted in a
circle, which was non-standard and took a bit of training by the operator.
The sending contact was opened by depressing a key, and remained open until
the selecting arm reached that key after leaving its rest of STOP position.

"205. Meanwhile, the selecting arm at the receiving Printer was similarly
seeking the printing point. When the line closed, it was there, so the
printing hammer struck the rotating typewheel, printing the character. The
Printer typewheel was inked, much as the old BLUE and GREEN code printers
had been. The inking roller can be seen at the top of the printer, with the
typewheel under it. then comes the printing tape, the supply roll of which
is at the bottom. The printing hammer is just under the tape and print
wheel, and moves upward to cause printing. The system was very simple and
therefore low cost, but only a limited number were made. "
------------------------------------------

I will send Brooke some pictures of the TX unit and he can put them on his
site.

The only problem in synch on the M36 was how to get the TX & RX back to the
home position.  Perhaps this was done through the SPACE function??

have fun,

Duncan