I cannot believe that no one has mentioned that "TIP and RING" came from, you guessed it, plugboard terminology! And of couse there was also the "sleeve". I assume (and you all know where that gets you) that the sleeve was used for all sorts of signaling functions, but I can't confirm that. Can anybody?
John C.

When I was young, I was Liberal. As I aged and wised up, I became Conservative. Now that I'm old, I have settled on Curmudgeon.