Message of Jerry : "The Drake 584-A is called a phone patch or in other words a device used to couple audio to and from the telephone line to the radio receiver and transmitter.  Phone patches were quite common when I was first introduced to amateur radio in the 50's.  Many men in the armed services were able to talk to their families over radio links using ham radio and these devices."

Message from Sindre TORP: "The High Patch incorporates a special bifilar transformer. With the NULL LINE control it is possible to balance out the signal which would otherwise pass through the Patch from the receiver to the transmitter. The balance will change from each circuit you select; that is, each new call may require small adjustment for best balance. The better the balance the less tendency for the receiver to trip the transmitter. The user-manual shows a typical installation using Collins KWS-1 and 75A4."