For the money, this is an exceptional product. The description says it is a circuit breaker location device, however,You can also use it to three circuits throughout a building as long as it is on the same circuit. This product works well and is very versatile in its use in testing electrical circuits.
The sound it makes starts going off a foot from the panel box. The sound hits it's highest level for at least three circuit breakers, so it is not precise. You shut off each breaker to see which one reduces the sound the most, that's the correct one. It works but I expected something a little more precise.
Still, it allows me to work by myself so I am happy I purchased it.