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:
Aug. 16, 1977
Filed:
May. 17, 1976
Glenn L Richards, Rochester, NY (US);
Stromberg-Carlson Corporation, Rochester, NY (US);
Abstract
A tone receiver for detecting a Dual Tone Multi-Frequency (DTMF) signal includes first and second digital tone detectors for the high and low bands, respectively. These detectors are of the type which employ the period detection technique. Each detector has a set of outputs corresponding to the valid tones in the respective band. A latching flip-flop is associated with each output of each detector. A coincidence timer is provided to insure that there are outputs from each of the detectors for a predetermined duration of time. The coincidence timer is reset by any change of any of the latching flip-flops from a state representing absence of the tone to a state representing presence of such tone. The latching intervals are determined by zero-crossings, which define the periods involved in the period detection operation.