Bi-directional multi-frequency ripple control system
Patent 4868539 Issued on September 19, 1989. Estimated Expiration Date: 
August 24, 2007. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.
August 24, 2007. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.Patent ReferencesMethod and apparatus for transmitting intelligence over a carrier wave Load shedding control means Patent #: 4359644 InventorAssigneeApplicationNo. 07/089663 filed on 08/24/1987US Classes:375/344, Automatic frequency control340/310.12, Modulation technique340/310.14, Zero crossing340/310.16Bi-directional (e.g., with transceiver)ExaminersPrimary: Moore, David K.Assistant: Fatahiyar, M. Attorney, Agent or FirmInternational ClassH02J 13/00 (20060101)Foreign Application Priority Data1984-04-17 AUAbstractA 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° 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. | |
