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:
Dec. 12, 1989
Filed:
Nov. 04, 1987
Applicant:
Inventors:
Assignee:
Control Data Canada Limited, Ottawa, CA;
Attorney:
Primary Examiner:
Assistant Examiner:
Int. Cl.
CPC ...
G08B / ; H01P / ;
U.S. Cl.
CPC ...
340552 ; 333237 ;
Abstract
An intrusion detection system of the type using cables arranged along a perimeter to be protected and sensing changes in the electrical field around the cables caused by the presence of an intruder. The cables are divided into sections or blocks and typically only one of the sections is energized at any time. The variations caused by an intruder at the selected sections are transmitted through the intervening section to the receiver portion of a transceiver located at one end of the cables. This indicates in which section intrusion has occurred. The system uses continuous wave excitation whereby the expense and complexity of high speed switching and timing of r.f. signals are avoided.