I will describe this device and let one of you CAD experts draw it.
Here is the parts list with Radio Shack PNs
Three jumper cables with alligator clips, Black, Red and Yellow with one clip removed on each cable 278-001.
One 6 to 18volt dc Piezo buzzer 273-068 (or similar)
Two 9 volt battery snap on connector units 270-325
Two standard 9 volt batteries
The Black lead is attached to the negative side of the Piezo Sounder with the alligator clip the loose end.
The Red lead is attached to the positive side of the Piezo Sounder with the alligator clip the loose end.
The two 9 volt batterys are connected together in series to make an 18 volt unit.
The positive lead from the 18 volt unit connects to the positive of the Piezo Sounder. The negative lead connects to the Yellow lead with the alligator clip the loose end.
DO NOT USE THIS ON 110 V AC CIRCUITS!!!!!!!!!!! YOU WILL GET HURT!!!
Using the noisy little monster:
The Black clip is attached to the chassis ground of you vehical. If you are hunting a short in a wire connect the Yellow to the wire and start moving the suspect wire around. When you rub the bad spot in the wire against the chassis ground the sounder will sound. This is nice because the sounder can be 30 feet away and you will hear it make noise when you find the short.
If you are checking for voltage on a wire, clip the Black lead alligator clip to chassis ground and use the Red lead to check the wire you are working on. If voltage is present you get noise. Want to check your brake light wiring, connect the Black lead to chassis ground in the trailer stop light and Red to the hot side of the bulb holder, hit the brakes and you can hear the sounder easily.
Want to check a bulb/fuse, pull the bulb/fuse and put the Black lead to the center tap of the bulb/fuse and the Yellow to the outer case/other lead of fuse. If you get noise the bulb/fuse is good. Is a wire shorted? Connect the Black clip to one wire and the Yellow clip to the other wire, shake.wiggle or short the wire at the other end. Noise equals a short.
I have used a unit like this for years in chasing down bad wire in alarm systems. If you want to make it cute put it in a Radio Shack project box 270-1809, mine is just held together with about 5 ft of electrical tape.
DO NOT USE THIS ON 110 VOLT AC CIRCUITS!!!!!! YOU WILL GET HURT!!!
I hope I have written this clearly so everyone understands how this works and how to use it.