[GreenKeys] Is this part this?

[E.]

In the M15/19 schematics, there are notes on how to bypass the relay by just moving/removing a few wires from their terminals.


> On Jul 28, 2025, at 11:03 AM, Duncan Brown <duncanancy at earthlink.net> wrote:
> 
> Windows XD,
> 
> The circled item on the schematic is a polar relay and it plugged into the socket in your picture.  The polar relay was the opto-coupler of the 1930s.  It isolated the machine's loop from the line.  
> 
> When these machines were originally developed (in the 1900-1930s) they were used on telegraph lines that could be 20 miles (or more) long.  Teletype Corp. used the generic term "Printing Telegraph" for their equipment up into the 1950s.
> 
> Since our TTY loops are measured in feet, not miles, we don't need the polar "Line Relay" option any more (though a lot of the M28 equipment still used them).
> 
> We generally just wire the selector magnets in series with the keyboard into our local 60 ma current loop, which is generally supplied by the modem/Terminal Unit/FSK Converter.  just make sure that the loop is limited to 60 ma before connecting it to the M19!
> 
> So you can just bypass and forget about the polar Line Relay.
> 
> Good luck & Have fun,
> 
> Duncan
> K2OEQ