[GreenKeys] Polar Relays

[Duncan Brown]

Harold,

All the Kleinschmidt Laboratories machines made for the military had 
SPDT switches for the keyboard and tape readers, so they could operate 
polar. But I never saw the polar connection used.  Polar was important 
for long DC lines, but not necessary when the machine is connected 
directly to a radio transmitter or AFSK modem.

All the Kleinschmidt Laboratories printers & reperfs (except for the 
TT-4) used a DC bias coil and a permanent magnet in the Selector magnet 
for faster response. ( The TT-4 was KLI's first model, in 1950, and it 
just used spring bias on the armature, but it was operator adjustable. 
You set it just like the Range control.)

Merry Xmas & Happy New Year,

Duncan
K2OEQ


On 25-Dec-21 13:56, Harold Hallikainen wrote:
> Long ago, I had a TU with a polar relay in it. As mentioned here, the
> mark/space decision was made in the relay. Also had a Teletype model 15
> with a polar relay in back. But the TU I ended up using a little over 50
> years ago used a 6L6 to key the loop. It also had the 88 mH loading coils
> in the filters.
>
> On generating polar signals, I think I've seen schematics of a TD and/or
> keyboard with SPDT switches so you could send polar.
>
> It would also be interesting if the selector magnet had a permanent magnet
> so the coil current could attract or repel the armature instead of using a
> spring to return the armature.
>
> Harold
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