Abstract: 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 of the waveform. At each appliance a microprocessor unit counts the number of successive pulses in a predetermined time interval and operates an electronic switch if the received count reaches a predetermined number, which may be different for different loads thereby enabling selective control of the loads. Provision is made for automatic restoration of supply if the overall energy consumption falls. Provision can also be made for automatic resumption of supply after a predetermined time interval.

Abstract: In an a.c. electricity power supply system, to guard against a "blackout", that is to say a cumulative supply failure caused by a fault leading to generating stations being overloaded and having to cease supplying a network, consumers are each provided with means responsive to the supply frequency and operative to reduce or cut out the consumer's load when the supply frequency falls below a predetermined value, which may be different for different consumers.

Abstract: An electrical energy consumption meter for use on a consumer's premises has data processing means responsive to the sensed voltage and current and to data such as tariff rates and clock information, for computing and displaying charges in monetary terms. A data link with the utility enables the utility to make use of this information and to add hire purchase commitments, etc. to the charges for energy consumption and also to enter credits for payments received. The data link may include provision for credit transfer by the consumer. Coin or token prepayment facilities may also be provided.

Abstract: In an electrical power distribution system, a consumer has a control unit comprising a plurality of solid state switches in supply leads to a plurality of separate load circuits, a microprocessor responsive to the magnitude of the total current drawn by the consumer from the supply and arranged to control the various switches so as to limit the total current or power in accordance with a priority program set into the microprocessor. The consumer can thus control the manner of use of the supplied power within a maximum demand limit. This overall maximum demand limit may be predetermined in accordance with an agreed supply tariff or may be remotely controlled by the utility.