How do you know which fuse protects which outlet?

Traditionally, to find which circuit breaker or fuse controls which lightswitch or wall outlet, you would plug a loud radio into an outlet and then go to the main panel and unscrew every fuse, or trip ever circuit breaker, until the radio went dead. And then there's yelling... 'Is that the one?'. At least the loud radio is a surefire technique, but long and troublesome, not to mention all the clocks that you just messed up.The telephone industry first developed gadgets that allow the repairman to identify the two ends of the same telephone wire. The installer would plug a little transmitter into one end of the line and it would sent out a radio signal along the wire. Back at the junction box, he would probe with a receiver until he picked up the signal, telling him which wire was which.For electrical wires, it is even more sophisticated, but now priced for the homeowner. You plug a special transmitter into an outlet, or a light socket adapter. Back at the fuse or breaker panel, you pass an electronic wand over the breakers until it beeps and points to the right wire. You don't even have to turn anything off. These were great gadgets but often didn't work because of interference in the lines.There are now a couple of reasonably priced detectors that work very well. "Circuit Detective"

and "Zircon's"

Circuit Breaker Finder. I've found a couple of electrical lines that still had too much static, but they work dead-on most of the time. Remember that all electrical work requires a permit, some provinces allow homeowners to do their own electrical work and some provinces require licensed electricians to carry out all such work. Click here for information on the LEGALITY OF DIY ELECTRICAL WORK.