The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Oct. 16, 1979
Filed:
Nov. 23, 1977
Richard F Challen, Lynchburg, VA (US);
Terry N Garner, Forest, VA (US);
General Electric Company, Lynchburg, VA (US);
Abstract
The prior art tone detector shown in U.S. Pat. No. 3,962,645 provides a repetitive sequence of vector signals at a predetermined or selected rate determined by the desired tone frequency to be detected. Each vector in the sequence has a different phase or angular direction. One vector in each sequence is selected at a time corresponding to a selected (usually zero) point in each cycle of received tone frequency. If the sum of a number of selected vectors exceeds a threshold, an indication of the desired tone is provided. In some tone detectors a phase shift in the tone can indicate a selected condition. Such a phase shift is detected by counting the number of vectors which are produced after the phase shift, whose magnitude added to the magnitude of the vectors produced before the phase shift exceeds a threshold, and whose sign differs from the sign of the vectors produced before the phase shift. When the count reaches a predetermined number, a phase shift indication is provided.