Tracer Products TP-9370 Marksman Ultrasonic Diagnostic Tool Ultra-sensitive electronic circuitry detects sound significantly beyond the range of the human ear Self adjusting AGC (Automatic Gain Control) circuitry automatically compensates for fluctuations in signal strength 10 bar LED intensity indicator helps pinpoint the exact problem source Precision engineered air and contact probes optimize receiver versatility Special emitter produces ultrasonic pulses to help receiver check for faulty seals, gaskets and weather stripping in passenger cabs, trailers and other non-pressurized enclosures