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:
Jan. 18, 1983
Filed:
May. 01, 1981
William J Lautzenheiser, North Billerica, MA (US);
American District Telegraph Company, New York, NY (US);
Abstract
In an intrusion alarm system, an anti-tamper system for detecting the bridging and removal of sensors connected in parallel along an interconnection cable includes means at each sensor for detecting open circuits on or shorting between any of the lines of the cable. Each sensor is provided with a resistance element and the resistance elements are connected in series by virtue of connection to the cable. Should any of the lines be cut or shorted, regardless of any bridging attempt to remove the sensor from operation, this condition is sensed and the series connection for the resistors is interrupted. This causes an imbalance at the comparator utilized to sense the combined impedances of the resistance elements and an alarm condition is indicated. If an attempt is made to bridge the line connecting the resistors together, the removal of the bridged resistor also causes an imbalance at the comparator which results in an alarm indication.