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. 03, 1977
Filed:
Jan. 12, 1976
Charles Elmer Jones, Jr, Fairfield, NJ (US);
William Frederick MacPherson, Warren, NJ (US);
Bell Telephone Laboratories, Incorporated, Murray Hill, NJ (US);
Abstract
A telephone ringer isolator for isolating ringers and extending ringing range on a multiparty telephone line or for range extension only on single party lines is disclosed. The circuit includes a detector circuit for detecting the direct current superimposed on an alternating current ringing signal. A pair of biasing circuits for transistors are enabled by a properly poled ringing signal appearing between tip and ring conductors. When the transistors are enabled, a capacitor is charged to trigger a silicon-controlled rectifier. When thus fired, the silicon-controlled rectifier enables a diode bridge gate to connect the ringer between one side of the telephone circuit and ground potential. Isolation between the input and output terminals is provided by the high collector resistance of the gating transistors.