Three-pin plug. The inside of a three-pin plug and a selection of fuses. A fuse consists of a fine wire which protects an electrical appliance from overload. If the current rises too high the fuse melts and breaks the circuit. The live wire has brown insulation, neutral blue , earth green and yellow. Each wire is connected to the appropriate plug pin. The 3-pin plug is used in the U.K. to connect domestic appliances and tools to the national 240 volt alternating current supply. The earth wire is an electrical connection between the appliance and the ground. In the event of a fault in the appliance the current flows to earth causing no harm to the user.