Communications: electrical – Condition responsive indicating system – Specific condition
Patent
1977-07-28
1979-11-13
Caldwell, Sr., John W.
Communications: electrical
Condition responsive indicating system
Specific condition
323 17, 325186, 340564, G08B 1324
Patent
active
041745183
ABSTRACT:
A quasi-stationary electric field is produced by means of an oscillator which produces an output frequency in the range of from 1-40 KHz and whose output is connected via a field voltage amplifier to a field wire which is mounted on and suspended between a plurality of fence posts by means of insulators and extends along at least a portion of the perimeter of an area to be protected. The electric field is detected by an antenna or wire whose output is connected to an AM detector via an amplifier. The output of the AM detector is connected to a high gain voltage amplifying and filtering arrangement so that at the output of this high gain amplifier only signals within the relatively low frequency range of from 0.2 to 2HZ associated with movement of an intruder are present. The output signal from the high gain amplifier is fed to a threshold circuit which produces an output signal whenever the input signal thereto exceeds a predetermined threshold value, and this output signal is fed to an alarm producing circuit. The output voltage of the field voltage amplifier is regulated to prevent changes of same due to environment caused changes in the impedance of the field wire from resulting in a false alarm.
REFERENCES:
patent: 2956269 (1960-10-01), Schmidt
patent: 3047849 (1962-07-01), Hansen
patent: 3237105 (1966-02-01), Kalmus
patent: 3644832 (1972-02-01), Sherman, Jr.
patent: 3778807 (1973-12-01), Ralston
patent: 3790878 (1974-02-01), Brokaw
patent: 4064499 (1977-12-01), Geiszler et al.
Caldwell Sr. John W.
Nowicki Joseph E.
Stellar Systems, Inc.
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