Turn off the breaker for the circuit, then use the tester to confirm ... "To check for voltage using double-prong voltage testers," advises Moinzadeh, "it is better to test both ways.

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 ...

If the response matches circuit will be considered as good. The quality of the chip depends, how thoroughly it is tested. In VLSI this is conquered by Automatic Test Equipment (ATE). Several types of ...