[GreenKeys] 1949 time division multiplex demo

[Brooke]

Hi Nick:

Here is a newer, much smaller and more capable unit.
https://prc68.com/I/MD1142.shtml

-- 
Have Fun,

Brooke Clarke
https://www.PRC68.com
axioms:
1. The extent to which you can fix or improve something will be limited by how well you understand how it works.
2. Everybody, with no exceptions, holds false beliefs.

-------- Original Message --------
> Date: Tue, 28 Oct 2025 15:11:35 -0400
> From: Nick England<nick at navy-radio.com>
> To: Greenkeys<greenkeys at mailman.qth.net>
> Subject: [GreenKeys] 1949 time division multiplex demo
> Message-ID:
> 	<CAB55hNcZ46hJJsbXptVk1UtRiGhW-Z-vOu0amGBYxoEJuXapDg at mail.gmail.com>
> Content-Type: text/plain; charset="utf-8"
>
> https://www.navy-radio.com/rtty/fgc5/fgc5-proto-4901.jpg
>
> photo caption - Electronic Time Division Multiplex Unit with attached
> battery of four Teletype transmitters. The Electronic Time Division
> Multiplex rearranges the output of two to four teletype machines so that
> the signals originated by those machines are transmitted over a single
> radio channel by a single radio transmitter, simultaneously for all
> practical purposes. The apparatus is divided into transmitting and
> receiving units. As messages are fed into a battery of four teletype
> transmitters hooked into the ETDM each is compressed in time, sorted into
> the proper time channel, mixed with the other signals, and fed into the
> radio transmitter. At the receiving end, the process is reversed and the
> signals, unscrambled, are fed into the teletype printers essentially at the
> same time as they are transmitted. Since each teletype transmitter can send
>   at speeds of 75 words per minute, this means a total of 300 words per
> minute transmitted. The Electronic Time Division Multiplex is calculated to
> make the best possible use of available radio frequency channels in
> military operations.
>
> The sign in the photo says that it is being tested on a 6000 mile RTTY loop
> DC-SF-DC.
>
> More info on this AN/FGC-5 system is at
> https://www.navy-radio.com/rtty-mux-fgc5.htm
>
> Nick England K4NYW
> Chapel Hill NC
> www.navy-radio.com

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