Abstract: A bidirectional ripple control system in which a code comprises an audio frequency signal superimposed on an electric power distribution system by an LC resonant circuit, controlled by a transmitter crystal oscillator which controls the signal frequency. A receiver has a pair of synchronous filters driven by a receiver crystal oscillator 90 degrees out of phase with each other. The outputs of the filters are squared and summed to form a single output independent of phase. For discrimination the output frequency of each synchronous filter is compared with a set level and the incoming signal is rejected if this frequency exceeds the set level. This system provides a very narrow band frequency detector for the receivers and enables the use of a large number of closely spaced frequencies for the formation of signalling codes. The system provides a means for bidirectional communication on an existing power distribution network.

Abstract: A ripple control system in which an audio frequency signal is superimposed on an electric power distribution system wherein the receiver has a pair of lock-in amplifiers driven 90.degree. out of phase with each other, the outputs of which are squared and summed to form an output independent of phase. For discrimination, a microcomputer is programmed for logically examining the time between zero crossings of each of the outputs of the lock-in amplifiers so as to check the output frequency thereof and completely reject the incoming signal when the output frequency exceeds an acceptable level. This system provides a very narrow band frequency detector for the receivers and enables the use of a large number of closely spaced frequencies for the formation of signalling codes.

Abstract: An electrical information transmitting means for consumer load control comprises a transmitter which transmits a coded signal through the conductors of an alternating current electrical distribution network as a sequence of wave-form distortions to a receiver which decodes the signal. The receiver comprises two correlators connected in quadrature, and the transmitters and each correlator synthesize synchronous signals from the power frequency, all of which is locked thereto. The D.C. voltage outputs of the correlators are squared and summed so that the receiver is independent of phase angle.