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:
Jan. 06, 1976
Filed:
Dec. 30, 1974
Donald W McLaughlin, Bolingbrook, IL (US);
David Q Lee, Chicago, IL (US);
GTE Automatic Electric Laboratories Incorporated, Northlake, IL (US);
Abstract
A precise tone injection circuit for injecting tone signals to a constant current junctor circuit in a two-wire balanced circuit. The tone injection circuit includes a pair of transistors operating as constant current sources feeding the respective ones of the two wires. A phase splitter amplifier couples a tone signal to the base electrodes of the transistors to change the current through their collector electrodes via the emitter circuits thereof at a rate and frequency of the tone signals at the base. Since a two-wire balanced circuit is used, and the injected signal currents to each wire are 180.degree. out-of-phase, in-phase signals, that is, noise and voltage fluctuations, are reduced or rejected.