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. 13, 1977
Filed:
Jul. 27, 1976
Richard H Greischar, Chicago, IL (US);
Extel Corporation, Northbrook, IL (US);
Abstract
An isolated line switching circuit for direct connection of a telephone, teleprinter, or like telecommunication instrument to a transmission line, comprising a solid-state optical cell including a light-actuated optical receiver that generates an electrical current when illuminated by an associated light-emitting device (LED), and a switching transistor having its emitter-collector discharge path connected in series with the transmission line; the optical receiver is connected to the base and emitter of the transistor to drive the transistor conductive when the LED is energized by an actuation signal initiated in response to a ring signal. A high-resistance emitter-to-base circuit for the transistor drains the collector leakage current (I.sub.CBO) and maintains a high off resistance even at high temperatures.