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. 30, 1988
Filed:
Oct. 22, 1987
William I Chen, Bedford, TX (US);
Philip Dillon, Arlington, TX (US);
Glenn Yancey, Burleson, TX (US);
Reliance Comm/Tec Corporation, Chicago, IL (US);
Abstract
A circuit for increasing the apparent inductance presented by a transformer to a differential signal. The circuit may be used in a battery feed interface circuit for providing battery power to a subscriber's telephone or in a current sink interface circuit for providing a low impedance DC loop closure toward a telephone line feed circuit while maintaining a high impedance for differential AC signals. In either usage the inductance multiplier circuit always multiplies the primary inductance of the transformer by a factor which is one plus a positive number. The transformer has three windings. The multiplication is accomplished by a current source which provides to the third winding a current which flows therein in a manner so as to oppose the current flowing in that winding due to the voltage induced in that winding when the first and second windings are excited by the differential AC signal.