Communications: electrical – Condition responsive indicating system – With particular system function
Patent
1981-05-01
1983-01-18
Caldwell, Sr., John W.
Communications: electrical
Condition responsive indicating system
With particular system function
340507, 340508, 340510, 340511, G08B 2900
Patent
active
043694365
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.
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American District Telegraph Company
Caldwell Sr. John W.
Crosland Donnie L.
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