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. 01, 1977
Filed:
Feb. 13, 1976
Carl E Atkins, Montclair, NJ (US);
Francis A McGuirk, Jr, Chatham, NJ (US);
Wagner Electric Corporation, Parsippany, NJ (US);
Abstract
A keyable control circuit sequentially connects a widely swept fm rf signal to sensing coils at a plurality of detection locations. While rf energy is fed to one of the sensing coils, all other sensing coils are gated off. A resonant detector generates a first signal when an external keying circuit containing a tuned circuit, resonant at a correct first frequency, is inductively coupled to one of the sensing coils. A time-gated envelope detector generates a second signal when the external keying circuit contains a second tuned circuit resonant at a correct second frequency. When the first and second signals are simultaneously present, gating circuits generate a control output signal which may be used to unlock a door or perform other functions access to which is restricted to those possessing keys.