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:
Jan. 20, 1976
Filed:
Aug. 12, 1974
Robert Lawrence Carbrey, Boulder, CO (US);
Bell Telephone Laboratories, Incorporated, Murray Hill, NJ (US);
Abstract
A method and apparatus for detecting multifrequency tones in a received signal by summing aperiodic samples and without using bandpass filters. In a receiver capable of detecting m different tones each comprised of n different frequencies, the apparatus performs m parallel summations each of 2.sup.n samples of the received signal. Each summation corresponds to a different detectable tone. In each summation, an initial sample is followed by samples delayed from it by respective half-periods of the frequencies comprising the corresponding tone and by samples delayed from the initial sample by combinations of different ones of such half-periods. The detection of a particular tone is indicated when the corresponding sum is zero and all other sums have finite values.