Fishman Voltmeter, 3 wires?

It is where you hook the deep line up to, this for all you non fishermen is a weighted line that you attach your primary fishing line onto. It is then cranked down to whatever depth you want it to go to (within the limits of the deep lines cable). It is primarily used when fishing for Salmon for us here on the wet (west coast).

PS, Dani, I had a noise complaint from a security guard in Victoria, seems those subs of yours have a habit of transmitting copious amounts of bass through concrete walls.