I have an old metal detector that has speaker only for output.
It makes constant noise as there is no discrimination knob. I'd like
to wire a headphone jack so my kids can detect with it without
annoying everyone.

I purchased Radio Shack 274-248 jack, and am looking for a schematic
or instructions for how to wire it in. Obviously the speaker has 2
wires, but the jack has 3 terminals. What wires go where?

-??