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:
Jun. 03, 1980
Filed:
Mar. 03, 1978
Applicant:
Inventor:
Robert D Williamson, Pembroke Pines, FL (US);
Assignee:
Other;
Attorney:
Primary Examiner:
Int. Cl.
CPC ...
G08B / ;
U.S. Cl.
CPC ...
340572 ; 340505 ;
Abstract
A high frequency generator projects an electronic wave into a surveillance area to establish a first field. At least one control zone is set up within the surveillance area by two low frequency (LF) generators. The first LF generator establishes a second field in the control zone. The second LF generator establishes a third field only at a control zone margin, thereby defining the limits of the control zone. Presence within the control zone of a transponder causes reradiation of a signal comprised of the high frequency and LF signal, which provides an output signal. Additional control zones may be set up within the surveillance area by the addition of further LF generators.