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. 19, 1990
Filed:
Sep. 20, 1989
Kenji Takato, Kawasaki, JP;
Toshiro Tojo, Kawasaki, JP;
Kazumi Kinoshita, Kawasaki, JP;
Yuzo Yamamoto, Kawasaki, JP;
Fujitsu Limited, Kawasaki, JP;
Abstract
A battery feed circuit including a main battery feed part and its peripheral circuits provided in a line circuit of a switching system. The peripheral circuits include the following: First, a means for forming a low impedance with respect to in-phase signals, simply realized by a capacitor; second, a bias circuit able to suppress the entry of power source noise and easily switch magnitudes of bias voltages and polarities, realized by a bias voltage generating means, a buffer means, and and AC bypass capacitor; third, a battery feed current control circuit able to suppress overflow of battery feed current when the distance to the subscriber is short, which detects an overcurrent component above a predetermined value, and, in accordance with the same, changes the bias voltage; fourth, a battery feed current supervising circuit able to detect current in both the forward and reverse directions, realized by an emitter-follower pair and a voltage/current converting resistor; fifth, a circuit for detecting bidirectional battery feed currents at a high precision, which is formed by forward direction and reverse direction current detection means provided with V.sub.BE cancelling means; and sixth, an overcurrent protection circuit, which changes the voltage applied between the inputs (+,-) of a transconductance amplifier forming the main battery feed part in accordance with an excess voltage.