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. 02, 1979
Filed:
Apr. 28, 1977
Joseph S Feng, White Plains, NY (US);
International Business Machines Corporation, Armonk, NY (US);
Abstract
The duty cycle of an AC telephone off-hook signal is measured by means of comparing it with the duty cycle of a known AC signal having a duty cycle of 0.5 because it has a DC component of zero. Measurement of the duty cycle in a telephone off-hook detector application involves measuring the DC portion of the signal on a pair of telephone lines from a telephone handset to an exchange. A high frequency master clock oscillator with a much higher frequency than the basic ringing voltage is used. An input signal is used to gate clock pulses to a counter when the input signal is positive. At the end of a predetermined number of clock pulses, the counter is gated into memory connected to a decoder for transmission of the decoded signal to the exchange for appropriate action.