Mains voltage test circuit - gives visual or audible warning of voltage levels relative to earth potential

摘要

The test circuit is to check mains voltages and consists of an optical or sound indicator with a current limiting resistor mounted in series. A capacitor (4) is charged and discharged and operates the indicator in alternate cycles. The example given uses a resistor (3), a neon (9) as indicator and diodes (5, 6, 7 and 8). The resistor (10) is provided to protect the neon. The circuit is suitable for use on its own or within a larger test circuit for checking voltage levels between live and earth lines without endangering the operator.