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. 07, 1990
Filed:
Oct. 12, 1989
Applicant:
Inventors:
Reinhard W Rosch, Richmond, CA;
Stanley D Rosenbaum, Ottawa, CA;
Assignee:
Northern Telecom Limited, Montreal, CA;
Attorneys:
Primary Examiner:
Assistant Examiner:
Int. Cl.
CPC ...
H02H / ; H04M / ;
U.S. Cl.
CPC ...
379412 ; 361102 ; 361119 ; 361 56 ;
Abstract
A telephone subscriber line is connected to a SLIC via contacts of an isolation relay. Line voltage on the line side of the relay contacts, and line current on the SLIC side of the relay contacts, are detected during opposite polarity half-cycles of an a.c. fault on the line, and the contacts are opened to protect the SLIC if the voltage and/or current is excessive. The interruption of current causes the line voltage to rise to maintain the protection for the duration of a fault.