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. 27, 1977
Filed:
Dec. 29, 1975
John W Walter, Manhasset, NY (US);
Other;
Abstract
An AC alarm system for protection against unauthorized intrusion having an alarm which consists of two pairs of adjacent bridge arms, each having at least one fixed resistor and a normally open switch shunted across at least one of the fixed resistors. The switches are normally open in a safety condition of the system and adapted to be closed during an unsafe condition. A variable resistor is also connected in series with one or more of the fixed resistors for balancing the bridge circuit. An AC transformer is provided having a secondary winding connected to opposite points of the bridge arms and two detection latch circuits are each connected at another of opposite points of the bridge arms for detecting a change in the resistance values of pairs of bridge arms and for producing a current in response to that change in order to actuate an alarm.