[GreenKeys] An Introduction to Teleprinters and Punched Tape Equipment

[Jim Haynes]

It's interesting that the 3-headed transmitter-distributor so closely
resembles the Teletype product. (page 32 and following)  I wonder if
they were making the Teletype design under license, or if they were
making a different but physically compatible device.  Or maybe by
the time they were making it they didn't need a license, as the
Teletype product goes back to the 1940s and patents would have
expired by then.

There is a precedent for a physically compatible design.  Back in WW-II
days the U.S. made the SCR-522 VHF aircraft transmitter-receiver.  It
is physically and plug-compatible with an English radio, but is
completely different inside.  My understanding is that the radios were
interchangeable in airplanes, so long as you interchanged the whole radio.