Residual Current Devices (RCD)
This is a device for human safety rather than solely protecting computer equipment and its function is to minimise the possibly of injury through electric shock. An RCD works by detecting if electricity is 'leaking' from a circuit and if so it breaks the circuit.
Most RDCs are combined with a circuit breaker and so will protect equipment in the case of an overload.
Typically, RCDs can be tested by pressing a testing button with should cause the device to operate as if a dangerous leakage had occurred. If the device operates properly, it can be used in a live environment and will perform its function. RCDs should be checked on a regular basis to make sure that they are still functioning properly.
Click on this link to review the wiki resource on RCDs.
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