An implantable microstimulator system employs a miniature ferrite-cored coil contained with an hermetically sealed housing to receive control signals and operating power from an RF telemetry system. The tiny coil receives the electromagnetic energy which is transmitted from a non-implantable transmitter...http://www.google.co.uk/patents/US5314458?utm_source=gb-gplus-sharePatent US5314458 - Single channel microstimulator
