To enable a consumer of electrical energy to effect control of total energy consumption by various individual appliances and loads, each individual load has a control unit, conveniently in a plug top, which responds to pulses broadcast on the power supply wiring in the form of short duration interruptions...http://www.google.fr/patents/US4471232?utm_source=gb-gplus-shareBrevet US4471232 - Method of and apparatus for controlling loads on an electrical power supply
Method of and apparatus for controlling loads on an electrical power supply
