Designed to meet IEC (International Electrotechnical Commission) standards and colour coding system. The configurations for plugs and receptacles are single-rated which assures proper mating of devices with the same voltage and amperage. So it is impossible to couple a plug and receptacle of different voltage and/or amperage ratings to avoid causing damage to the equipment or even personal injury. The receptacles with Interlock device eliminate the possibility of making or breaking the circuit under load or making a haphazard connection.