Every electrical current generates a magnetic field, so a non-contact voltage tester can detect current in a conductor ...

See? Good and evil. An RCD (or GFCI in the States) is a kind of circuit breaker that trips when the amount of current in the hot and neutral mains power lines aren’t equal and opposite ...

Also, the tester is built to be tough and can ... build quality ensure that it will last through repeated use. ET450 Advanced Circuit Breaker Finder And Wire Tracer Kit The Klein Tools ET450 ...