INTRUSION_ALARM

Published:2009/7/16 6:00:00 Author:Jessie | From:SeekIC

Circuit stops oscillating when intruder approaches antenna surrounding area being protected. Uses weak oscillator with relay tube that is biased to cutoff by some of oscillator output. Additional capacitance caused by intruder stops oscillator, removing bias and making tube conduct and actuate relay to sound alarm.-J. Markus and V. Zeluft, Handbook of Industrial Electronic Control Circuits, McGraw-Hill, N.Y., 1956, p 19.



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