Speaking of cables, did you know phono quitar cables actually originate from the telecom industry? That's why they're called PHONE-o cables. Operators used those cables to connect calls. In phone terminology we still talk of "tip" and "ring". Tip is ground (sorta) and ring is -48v (-54v float). When doing a line test to determine if there is an issue with a phone line it will show resistance and capacitence between tip to ground, ring to ground and tip to ring. People who really know their stuff can tell what type of trouble may exist on the line based on different conditions. Very low capacitance and no short can mean open at the CO, for example.
Those actual cables arn't use that much for regular phone circuits but are used for data circuits at panels called a DSX panel (not to be confused with door security access panels which are also called that). Typically they're just used during testing phase though, 4-wire connections will be run, similar to what is done at the MDF with 2 wire connections.
This is your TIL for today.