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:
Dec. 25, 1984
Filed:
Sep. 16, 1982
Kunio Nagashima, Tokyo, JP;
Nippon Electric Co., Ltd., Tokyo, JP;
Abstract
A subscriber line circuit comprises a controllable DC to DC converter (41) for producing a converter output signal which becomes a loop signal comprising a DC signal and/or a communication signal of a communication frequency band. First and second voltage signals are dependent (51, 69) on the current and the voltage of the loop signal, respectively. One of the voltage signals is amplified (71) with different transfer functions at DC and in the communication frequency band. The converter is controlled (85-86) by an error between a first sum (81) of the amplified signal and the other voltage signal and a second sum (82) of a reference voltage (E.sub.O) and a signal supplied from an output (27) of an exchange. A subtractor (92) supplies a difference between the exchange output signal and the second voltage signal to an input (25) of the exchange. Preferably, terminals (16, 17) for connection to a subscriber substation are isolated at DC from terminals (18, 19) for connection to the exchange input and output.