The MT123 is a pocket-sized magnetic solenoid tester that responds to all kinds of magnetic fields. It is easy-to-use. Just touch the tip to an outlet or cord, when the tip glows red it indicates voltage in the line. Accessories: AAA Batteries Instruction Manual General Application: Testing operating solenoid valves in pneumatic and hydraulic control equipment. Testing relays with coils and electrically controlled solenoid valves in all types of vehicles and machineries. Testing solenoid valves when servicing oil burners, the test lamp lights immediately and without metallic contact when there is a magnetic field, e.g. and activated coil in a solenoid valve. The test lamp responds to all kind of magnetic fields – from alternating current to direct current and to permanent magnets. Features : Easy-to-use Built-in LED flashlight Red LED light with audible beeper indicator All outer surfaces are non-conductive for safety Detects AC current without metallic contact Test magnetic field (H): 63, 98, 401, 810