PROGRESSIVE ELECTRONICS inductive telephone line tester set

This pair are electronic testers that are (were, anyway) rather indispensable tools for telephone linemen -- that is, the guys that deal with the actual *wiring* associated with 'landline' telephones and equipment. This 200EP INDUCTIVE AMPLIFIER and 77HP THE TRACER in their custom fit belt holder are used together to allow 'tracing' of phone wiring -- the TRACER part is plugged or clipped onto a phone jack (or whatnot) at some location where it puts an audible 'signal tone' into one end of that pair of wires, then the INDUCTIVE AMPLIFIER can be used at a different point in the telephone wiring system to identify exactly which (of potentially many!) pair of those wires are the 'other end of the line', so to speak. (kinda literally, too?!) The term 'inductive' means that the amplifier does not need to be physically connected to any given wires or terminals it is testing for (though it can be) but instead can pick up the TRACER signal by simply being in close proximity to it/them -- the closer to the connection produces a stronger/louder tone from the amplifier probe.

I don't know for certain, but this set likely is from the 1990's or so, shortly before or during the period when cellular telephones were becoming common alternatives to landlines.