Single RCD (Safety Switch) Outlet Preventing Electrocution 10A 240V rated MS4013RCDs (residual current devices), also commonly called safety switches, are designed to cut the power in a fraction of a second in the event of a fault condition, thereby preventing electrocution. The electrics in your house may be too old to have RCDs installed, or you might want to use a power tool outdoors on an outlet that doesn't have an RCD fitted use this handy portable one instead. Buy one right now if you don't have RCDs already it's a lot