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:
Dec. 07, 1982
Filed:
Oct. 28, 1980
David G Agnew, Ottawa, CA;
Sorin Cohn-Sfetcu, Kanata, CA;
Northern Telecom Limited, Montreal, CA;
Abstract
A tone detector in the form of a digital correlator is disclosed in which PCM signal samples are delayed in a RAM for the correlation period. Using PROMs, the products of the current and delayed samples with samples of a sine signal at the frequency to be detected are produced, and their difference is cumulatively summed to produce a first accumulated signal. A second accumulated signal is similarly produced using samples of a cosine signal at the frequency to be detected, and an output signal indicating the presence or absence of the tone is produced from the sum of the squares of the two accumulated signals. The use of memories enables the detector to be readily multiplexed for detection of a plurality of tones on each of a plurality of channels.