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:
May. 13, 1986
Filed:
Dec. 28, 1983
Mitsutoshi Ayano, Tokyo, JP;
Kiyoshi Shibuya, Kawasaki, JP;
Shin-ichi Itou, Tokyo, JP;
Kenji Takatou, Kawasaki, JP;
Toshiro Tojo, Kawasaki, JP;
Fujitsu Limited, Kawasaki, JP;
Abstract
A battery feed circuit for a two-wire telephone subscriber line is miniaturized by an electronic integrated circuit without a transformer. The electronic battery feed circuit is composed of first and second operational amplifiers, output resistors, a DC voltage feedback loop, an AC signal feedback loop and a switching power supply. The switching power supply means is to control the power source voltage of the first operational amplifier, corresponding to the length of the subscriber line loop and the status of a telephone set in the loop. Low power consumption of the circuit is attained as follows. Most of power loss of the circuit can be separated as between the amplifiers and the output resistors. The loss of the output resistors are reduced by using small resistances, and the loss of the second amplifier is reduced by using a small DC bias. The loss of the first amplifier is reduced by setting its power source voltage to several volts lower than output voltage of the switching power supply. The switching power supply is composed of a zener diode, two comparators and a switching transistor circuit.