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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.:

US 3971898 B1

PDFFull Text
Date of Patent:
Jul. 27, 1976

Filed:

Mar. 14, 1975

Visual indicating control circuit in key telephone system

Applicant:
Inventors:

Tokuhisa Hijikata, Tokyo, JA;

Koichi Sekiguchi, Tokyo, JA;

Assignee:

Iwatsu Electric Co., Ltd., Tokyo, JA;

Attorney:

Oblon, Fisher, Spivak, McClelland & Maier

Primary Examiner:

Kathleen H Claffy

Assistant Examiner:

Randall P Myers

Int. Cl.
CPC ...
H04M / ;
U.S. Cl.
CPC ...
179 99 ; 179 / ;
Abstract

A visual indicator control circuit for use in key telephone systems is disclosed. The circuit includes a plurality of light emitting diodes connected in series and operated by a plurality of transistors having collector-emitter paths connected in parallel with the light emitting diodes. Circuits are provided for controlling the respective base electrode voltages of the transistors corresponding to the use status of each line to control the light emitting diodes corresponding to the on or off states of the transistors.

Find Patent Forward Citations

Hijikata, Tokuhisa. (1976). Visual indicating control circuit in key telephone system (U.S. Patent No. 3971898). U.S. Patent and Trademark Office. https://idiyas.com/patent/badge/3971898

Data source: USPTO (United States Patent and Trademark Office) public patent records. Weekly synchronization. How IDiyas builds this profile

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