An isolator switch is part of an electrical circuit and is most often found in industrial applications, however they are commonly fitted to domestic extractor fans when used in bathrooms in the UK. The switch does exactly what its name suggests in that it electrically isolates the circuit or circuits that are connected to it. Such a switch is not used normally as an instrument to turn on/off the circuit in the way that a light switch does. Either the switch isolates circuits that are continually powered or is a key element which enables an electrical engineer to safely work on the protected circuit. Isolator switches may be fitted with the ability for the switch to padlock such that inadvertent operation is not possible (see: Lock and tag). In some designs the isolator switch has the additional ability to earth the isolated circuit thereby providing additional safety. Such an arrangement would apply to circuits which inter-connect power distribution systems where both end of the circuit need to be isolated. Major difference between isolator and circuit breaker is that isolator is an off-load device, whereas circuit breaker is an on-load device.
