Electrical plugs. Two types of electrical plug and a switch. At centre is a standard electrical plug fitted with a fuse. This draws power at the normal mains voltage. The plug at left is a universal adaptor plug. It is both a rectifier (converting mains electricity from alternating current [AC] to direct current [DC]) and a transformer (reducing the voltage). It has been set to take the current from the negative output, and transform it to a 4.5 volts output (mains voltage in the UK is 230 volts). Many electrical devices require DC power. The switch is fitted with an accessible fuse that is easily replaced when needed.