Steelman 06400 Stethoscope Electronic TracerEAR Ultra sensitive microphone and amplifier providing full range of sound with no missing frequencies Isolates sound with no unwanted sounds bleeding in Pin-point noise and location of worn bearings and bushings, noisy valves and lifters, broken or worn gear teeth, faulty fuel injectors, wind or air leaks, and annoying squeaks and rattles Non-conductive - will not zap expensive computer circuitry Uses 9 Volt battery (included)