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. 02, 1978
Filed:
May. 24, 1976
Applicant:
Inventor:
Robert D Williamson, Pembroke Pines, FL (US);
Assignee:
Other;
Attorney:
Primary Examiner:
Int. Cl.
CPC ...
G08B / ;
U.S. Cl.
CPC ...
340280 ; 3402 / ;
Abstract
A high frequency generator projects an electronic wave into a control zone under surveillance to establish a first field. A frequency modulated (FM) generator is used for establishing a second field throughout the zone. A third field of the same FM carrier frequency, but with a different modulation, is established only at extreme ends of the control zone to define the limits of the control zone. Presence only within the control zone of a transponder causes the reradiation of a signal comprised of the FM signal and the high frequency signal, which in turn activates an alarm circuit.