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:
Apr. 23, 1996
Filed:
Apr. 21, 1995
Stanley A Gores, Kanata, CA;
Joseph F Darveau, Aylmer, CA;
Francois Y Tremblay, Hull, CA;
Stanley D Rosenbaum, Ottawa, CA;
Reinhard W Rosch, Richmond, CA;
Northern Telecom Limited, Montreal, CA;
Abstract
A two-wire telephone line is supplied with d.c. feed from a drive circuit including two amplifiers via which a transmission signal is supplied to the line. Output potentials of the two amplifiers determine a loop current on the line, which is monitored and used to control a supply voltage for the drive circuit, the amplifier output potentials being offset from the supply potentials by headroom voltages to accommodate the transmission signal. The resulting current limiting voltage control acts iteratively to converge the supply voltage and a target voltage which is inversely dependent on an amount by which the loop current exceeds a predetermined value, the rate of convergence being fast for high loop currents for rapid response and slow for small differences to provide stable operation. The headroom voltages can be increased to nearly the supply voltage to reverse the polarity of the d.c. feed while maintaining current limiting.