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:
Mar. 14, 1978
Filed:
Feb. 12, 1976
Frederick J Glenn, Arlington Heights, IL (US);
Cook Electric Company, Morton Grove, IL (US);
Abstract
An automatic number identification device is used in a telephone system to enable a telephone central office to identify from which of two parties on a two party telephone service a call is originating and is coupled to a pair of telephone lines extended from the telephone central office to one of the parties being served by the two party telephone service. A loop current sensor is connected in series relation with one line of the pair of the telephone lines forming a subscriber loop and detects when a specified loop current is present on the one line. When the loop current sensor detects such a loop current, a control circuit, energized by power derived from the telephone lines and coupled to the loop current sensor by a photo coupler, couples a resistive ground to both of the lines in the given subscriber's loop. The control circuit has an on-time delay so that ringing signals on the subscriber's lines do not effect the operation of the control circuit and an off-time delay so that dialing pulses are not distorted.