Rcd Controlled Circuits Switch. Press it in and you cause a temporary short circuit that should cut the power. Firstly turn off all the circuits that are protected by the device and try to reset it.
Plug the rcd into your electricity outlet plug your appliance into the rcd and you re all ready to go. Turn off all circuit breakers cbs that are controlled by the rcd that is tripping note if there are appliances that get upset by power being shut off and restored repeatedly turn these off until after the problem has been sorted eg a fridge or freezer. Check to make sure it is in fact an rcd and not just a circuit breaker which simply acts like a fuse.
This article may help you switch it back on.
An rcd is a sensitive safety device that switches off electricity automatically if there is a fault. Circuit breakers can look the same but an rcd safety switch will have a test button located on the front usually with a t symbol on it. It may be that al the circuits will turn back on and the rcd will be ok you will then have to try and identify the cause which may be as simple as a blown lamp. Plug the rcd into your electricity outlet plug your appliance into the rcd and you re all ready to go.
