Electrical and electronic testing equipment is used to ensure the safety of workers and the protection of equipment. It is primarily used to test for electrostatic discharge; continuity in electrical systems; and electrical inductance, capacitance and resistance in various components. ESD testing equipment ensures that ESD control devices are functioning properly and ensures protection against static electricity. ESD static meters measure static electricity on an object's surface. Continuity testers assess continuity in circuit breakers and other electrical systems. These devices are commonly handheld and use an LED light or buzzer to indicate a closed circuit and, therefore, a correctly functioning electrical system. LCR meters measure magnetic flux, electrical charges and the opposition to electrical currents in conductors.