Hi,

I have a very basic newbie question about the 500 phones. I have several 500s that I have acquired over the years, and I am starting to get them cleaned and working. I have noticed that some of them have cords with four wires red, green, black, yellow, while others have three wires, red, green, and yellow.

Was this a party line thing or simply an economic thing (three wire must be less expensive than four wire)? I know that the early princess phones needed the extra pair for the lighting voltage, but cannot figure this out.

Thanks,

Joe

Real comms took 200lb teletypes, hand keys, sounders, operators and cranked phones!