[GreenKeys] Polar Relays II

[Harold Hallikainen]

Thanks for all the info on polar relays! When in high school, I had a TU
that used a polar relay to compare the mark and space tone levels. I also
had a Teletype with a polar relay in back. The wiring harnesses in a
Teletype got really complex to allow for all the options. Basic operation
would require just 6 wires (2 each for motor, keyboard, and selector
magnets). But the machines also get a lot more complicated.

You mention the use of gas discharge tubes in some equipment. I remember
seeing NE-2 lamps in some terminal units. For example, the terminal units
on page 299 of the 1966 Amateur Handbook has a couple NE-2s that provide
hysteresis in the circuit.

To me, the most practical use of the polar relay is to interface a polar
telegraph circuit to the selector magnets in a machine.

Thanks for all the great history!

Harold
https://w6iwi.org