Got one of these in new condition in a trade recently. Just got around to checking it out. These things work great !! 7 different mic plug variations on front. Just plug and play. Built in speaker. Runs on 12V. 8 position terminal strip on side for sticking bare wires in for unknown wiring arrangements. There are other brands of these things too and they look pretty similar. May just be the one unit with differing brand names on them. I can't be they sell so cheaply. I think you can get them on ebay for like $32. Cheap price for nice multi-purpose tester.