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:
Nov. 21, 1978
Filed:
Dec. 12, 1977
John A Calder, Chicago, IL (US);
Richard M Rovnyak, Schaumburg, IL (US);
David Q Lee, Chicago, IL (US);
GTE Automatic Electric Laboratories Incorporated, Northlake, IL (US);
Abstract
A detector circuit for use in conjunction with a trunk circuit of a PABX telephone system interfacing with a central office providing for constant monitoring of normal or reverse battery application by the central office during the high impedance idle state or the low impedance busy state. In addition, the circuit provides for detection of: proper loop closure, electrically shorted tip and ring leads, open circuit condition of tip and ring leads or a grounded ring lead. Furthermore, the circuit indicates when current flow of proper magnitude is sensed during normal or reverse battery conditions.