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. 06, 1987
Filed:
Feb. 04, 1985
Ross McPherson, Denville, NJ (US);
Kenneth F Smolik, Morristown, NJ (US);
David J Thomson, Murray Hill, NJ (US);
American Telephone and Telegraph Company, New York, NY (US);
Bell Telephone Laboratories, Incorporated, Murray Hill, NJ (US);
Abstract
Supervisory audio tones received from a mobile telephone unit are converted from analog to digital form. The tone is then converted to a complex number by bifurcating the tone path and multiplying one path by a sine function and the other path by a cosine function. The complex numbers are accumulated and the frequencies where significant power exists is found using the discrete Fourier transform. If the power at an assigned frequency exceeds a threshold, the corresponding supervisory audio tone is declared to have been detected.