US Patent 7193335 Sensing socket assembly

A socket assembly enables a number of electrical appliances to be automatically isolated from, and reconnected to, an electrical power supply upon respectively switching off or on a “master” appliance. Generally, the assembly includes: a master electrical outlet and at least one slave electrical outlet, both connectable to a common power source; sensing means for sensing power drawn from the master electrical outlet; a controller operable to isolate the at least one slave electrical outlet from the power source when the sensing means detects a fall in power drawn from the master electrical outlet from a first, higher level to a second, lower level.