[GreenKeys] 1949 time division multiplex demo

[Duncan Brown]

  Eric's unit was made by the Morkrum Co. in about 1920.  Enclosed is a 
picture of a Kleinschmidt Electric Co. Model 20, also from about 1920. 
They were both manufactured for Western Union and the main difference is 
that the Kleinschmidt unit had a frame on the sides. The machines 
printed on a paper tape that was stored in a drawer beneath the printer.

There are plans on making a serial to parallel converter/driver for this 
printer in the April 1962 issue of
RTTY magazine, but it uses over 20 tubes!

Besides inventing the first practical teletypewriter in about 1880, 
Emile Baudot also invented Time Division Multiplex with a system of four 
TTY signals operating on a single wire.  This was a synchronous system 
and the printers for this system can be identified as they have 5 
selector magnets - one for each bit. This synchronous, TDM, system was 
used up into the 1930s.

In 1924, Morkrum and Kleinschmidt Electric combined to become the 
"Morkrum - Kleinschmidt Corporation."
This name was felt to be too cumbersome, and in 1928, the name was 
changed to "Teletype Corporation."  Morkrum had previously been using 
"Teletype" as a brand name.


Have fun,

Duncan
K2OEQ


On 10/28/2025 4:28 PM, Eric Moore wrote:
> Funny, I just snapped pics of this guy today.
>
> See the magnets along the top? There is a manual online I found, but 
> not expecting much luck resurrecting it considering the layer of rust.
>
> -Eric
>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: KEC_0278 Model 20A.jpg
Type: image/jpeg
Size: 48312 bytes
Desc: not available
URL: <http://mailman.qth.net/pipermail/greenkeys/attachments/20251028/3d7e7e9c/attachment.jpg>