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:
Nov. 17, 1998
Filed:
Oct. 17, 1996
Gyula Jakab, Nepean, CA;
Northern Telecom Limited, Montreal, CA;
Abstract
A telephone ringing signal generator includes a DC converter for producing high positive and negative voltages that define peak amplitudes of the ringing signal, which is produced by low pass filtering a generally trapezoidal waveform having these peak amplitudes. The generally trapezoidal waveform is produced by a level-shifting integrator at a frequency determined by a low voltage square wave supplied to the integrator. The integrator comprises a capacitor coupled between a virtual ground point and an output of the integrator and arranged to be charged with two opposite polarities in response to opposite transitions of the square wave, and a resistor via which the square wave is supplied to the virtual ground point. Buffers are provided for buffering the trapezoidal waveform supplied to, and the ringing signal produced by, the low pass filter.