This non-contact voltage detector features an analog feel. The closer the probe is to the voltage source, the louder and brighter the indicators become. Detects AC voltages without contact and features a bright red LED light and buzzer. With a 24VAC to 440VAC range of the SNCV1 offers technicians the ability to test thermostats and other HVAC/R parameter easily. Clips to your shirt pocket and is a quick source to find out whether that line is hot or not.