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:
Jun. 23, 1981
Filed:
Jun. 22, 1979
Gilbert M Ferrieu, Bievres, FR;
U.S. Philips Corporation, New York, NY (US);
Abstract
Subscriber line interface circuit for connecting a subscriber's telephone line to, for example, an automatic telephone exchange comprising a pair of amplifiers whose outputs are connected to the wires of the telephone line and which are fed by a d.c. voltage supply source. This supply source provides the telephone line with direct current via the amplifiers. In practice, the telephone line must be terminated by a symmetrical impedance of a prescribed value. To this end the interface circuit comprises means for determining the weighted sum of the current flowing through one and through the other wire of the telephone line such that the sum current is independent of the longitudinal currents in the telephone line. By means of an impedance, two antiphase feedback voltages are generated at the inputs of the amplifiers, these amplifiers then having a symmetrical impedance at their outputs.