Model 44SVD personal voltage detector is designed to detect high voltage from 2.5kV and up without physical contact. It detects 44kV from up to 30 feet away. As the detector is moved closed to the voltage-carrying conductor its AC sensor plate picks up the radiated electric field. Electric field is amplified and processed by the internal circuitry. Once the processed signal is above the threshold, it triggers the input of an integrated circuit, which turns on both the buzzer and LED. AEMC Instruments 200 Foxborough Blvd. Foxborough, MA, 02035