[GreenKeys] What is a polar relay?

[steve bennett]

 Nick,
  Thanks for the info.-Steve AD8CI
    On Saturday, April 3, 2021, 02:00:08 PM EDT, Nick England <navy.radio at gmail.com> wrote:  
 
 Telegraph and teletype signal lines could be neutral or polar. Neutral is off for Space and 60mA for Mark. Polar is 60mA flowing one way for Space and the other way for Mark. A polar relay was a fast and sensitive relay that could respond to polar signals. It also had a bias winding so it could be set to respond to neutral signals. Any time you wanted to isolate one circuit from another, or perform some sort of logical function, the polar relay was the answer. For example, the selector magnets in many teletype printers were not directly keyed by the signal line, but by a local loop supply keyed by a polar relay connected to the signal line. Nickhttp://www.navy-radio.com/manuals/tty/570-303-106-6412.pdf


On Sat, Apr 3, 2021 at 1:47 PM steve bennett via GreenKeys <greenkeys at mailman.qth.net> wrote:

Greenkeys,
What is a polar relay and how is it used in teletype?
Thanks,-Steve Bennett AD8CI
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Nick England K4NYW
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