This is a low-cost receiver that is tuned to 50-60 Hz. and picks up the electromagnetic wave when current is present in the cable. It will detect loaded lines where most others fail, because of advanced receiver circuitry and a precision wound antenna. Not only are low energy signals or waves detected, but also some low impedance grounded faults, underground transformers, and splices can be found. Operating the receiver/antenna "gun" and headphones is very simple. The AT9 comes complete with headphones and a foam lined carrying case designed for rugged protection of the instrument. An external loudspeaker box is available. The AT9 requires less than 1 amp load current to produce a locate 3 feet deep typically. A 100W light bulb draws about 8 amps.