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:
Dec. 20, 1977
Douglas C Smith, Rumson, NJ (US);
Bell Telephone Laboratories, Incorporated, Murray Hill, NJ (US);
Abstract
The disclosed T-type line compensation circuit reduces the gain and return loss variations when customer equipment is connected to a central office or PBX over telephone lines of various lengths. A linear resistor of a first series leg is thermally coupled, as a heat source, to a positive temperature coefficient (PTC) resistor of a second series leg. The shunt leg consists of a series connection of a bilateral zener diode, linear resistor, and varistor. The resistance value of both the second series leg and the shunt leg of the line circuit vary automatically with the direct current in the line to minimize gain variation due to telephone line length variation. The thermal feedback to the PTC resistor varies automatically with the direct current in the line to minimize return loss variations seen by the customer equipment.