A while back someone asked me  how I wired a polar relay to my military Dovetron. I finally put it together.

I used coax with a BNC on the Dovetron +/- 12V end and wired the relay end to a solder terminal strip. I used stranded hookup wire to connect to the relay. Since I did not have a socket and did not want to solder to the plug, I pulled wrap-around pins from an old octal tube socket, squeezed them tighter with pliers and pushed them on the

The shield of the coax is connected to pin 2 of the relay, the center conductor to to pin 6. Pins 3 and 8 are jumpered

to put the two windings in series aiding. The marking contact is taken from pins 1 and 4, In my system this goes to a  plug to patch it in to any loop with a loop supply. The relay is mounted on an aluminum plate to fit  a 4 inch square electrical box since the relay is mounted sideways, I made sure the contacts were horizontal so they would not be biased by gravity. It worked the first time.

I am attaching a drawing of the 255A from the New RTTY Handbook, page 71 and a photo of the installed relay patched into one of my loops.

Tom   N3CRK