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:
Feb. 02, 1988
Filed:
Feb. 05, 1986
U.S. Philips Corporation, New York, NY (US);
Abstract
A subscriber telephone set which comprises a multifrequency dialing tone oscillator, a microprocessor connected thereto for controlling selection of the tones produced thereby, and an acoustic signal element for producing a ringing sound corresponding to ringing tones applied thereto. The microprocessor prevents incorrect triggering of the acoustic signal element by noise voltages on the subscriber line by verifying that the amplitude of the ringing current received on the line exceeds a predetermined level, and also that the ringing current frequency corresponds to the frequency of a resetting signal internally generated within the microprocessor. Upon such verification, the microprocessor controls the dialing tone oscillator to generate a ringing tone which is applied to the acoustic signal element to cause it to generate a ringing sound, the dialing tone oscillator thereby also serving as a ringing tone generator for activating the acoustic signal element.