Properties:

An item specifically designed to test and/or monitor an electrical circuit and indicate its operating condition by means of a display, such as lamps or light emitting diodes. Examples of conditions being indicated are power on, no power, reversed polarity, open ground, open neutral, alternating current and/or direct current. It may or may not be used to indicate definite power line voltage ratings, such as 110, 220 and 440 volts. It is designed to be inserted in the circuit being tested. For items designed to indicate with out physical contact with the object being tested, see indicator, electrical potential. See also light, test, and voltmeter.