Perimeter alarm apparatus
First Claim
1. A perimeter alarm apparatus for guarding or monitoring a designated area to determine the presence or absence of designated persons or objects within the area, comprises:
- a transmitter having means for attachment thereof to the designated person or object;
said transmitter having electrical circuit means for continuously and cyclically producing a changing magnetic field, said electrical circuit means including a plurality of coils arranged angularly relative to one another and connected with means for alternately and sequentially energizing the coils whereby a plurality of changing magnetic fields of different polarity are produced to minimize the effect of different orientations of the transmitter;
a monitor for monitoring the presence of the transmitter and including a wire loop extending around the perimeter of the designated area;
monitor electrical circuit means connected with the wire loop for detecting the presence of a signal induced on the loop by the magnetic coupling between the transmitter and loop;
said changing magnetic field and wire loop being related such that a signal of proper strength is magnetically induced on the loop whenever the transmitter is within the area bounded by the loop, but when the transmitter is a predetermined distance beyond the boundary defined by the wire loop, a proper signal is not imposed on the loop; and
alarm means connected with said monitor electrical circuit means for indicating when the transmitter is not inducing a proper signal on the loop.
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Accused Products
Abstract
A perimeter alarm apparatus includes a loop of wire to be placed around an area to be guarded and electrical circuitry connected with the loop for detecting the absence of a signal imposed on the loop. The signal imposed on the loop is produced by a sending unit worn by a child, for example, who is intended to remain within the area bounded by the loop. As long as the child is within the area, the sending unit will induce a signal on the loop, but when the child moves beyond the loop a predetermined distance, no signal is imposed on the loop, with the result that an alarm is sounded by the circuitry.
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Citations
10 Claims
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1. A perimeter alarm apparatus for guarding or monitoring a designated area to determine the presence or absence of designated persons or objects within the area, comprises:
- a transmitter having means for attachment thereof to the designated person or object;
said transmitter having electrical circuit means for continuously and cyclically producing a changing magnetic field, said electrical circuit means including a plurality of coils arranged angularly relative to one another and connected with means for alternately and sequentially energizing the coils whereby a plurality of changing magnetic fields of different polarity are produced to minimize the effect of different orientations of the transmitter;
a monitor for monitoring the presence of the transmitter and including a wire loop extending around the perimeter of the designated area;
monitor electrical circuit means connected with the wire loop for detecting the presence of a signal induced on the loop by the magnetic coupling between the transmitter and loop;
said changing magnetic field and wire loop being related such that a signal of proper strength is magnetically induced on the loop whenever the transmitter is within the area bounded by the loop, but when the transmitter is a predetermined distance beyond the boundary defined by the wire loop, a proper signal is not imposed on the loop; and
alarm means connected with said monitor electrical circuit means for indicating when the transmitter is not inducing a proper signal on the loop. - View Dependent Claims (2, 3, 4, 5, 6, 7)
- a transmitter having means for attachment thereof to the designated person or object;
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8. A perimeter alarm apparatus for guarding or monitoring a designated area to determine the presence or absence of designated persons or objects within the area, comprises:
- a transmitter having means for attachment thereof to the designated person or object;
said transmitter having electrical circuit means for continuously and cyclically producing a changing magnetic field;
said transmitter attaching means connected with switch means in the transmitter electrical circuit means, said switch means being responsive to removal of the transmitter from the person or object for de-energizing the transmitter when the transmitter is removed from the person or object, whereby an alarm is given;
a monitor for monitoring the presence of the transmitter and including a wire loop extending around the perimeter of the designated area;
monitor electrical circuit means connected with the wire loop for detecting the presence of a signal induced on the loop by a magnetic coupling between the transmitter and loop;
said changing magnetic field and wire loop being related such that a signal of proper strength is magnetically induced on the loop whenever the transmitter is within an area bounded by the loop, but when the transmitter is a predetermined distance beyond the boundary defined by the wire loop, a proper signal is not imposed on the loop; and
alarm means connected with said monitor electrical circuit means for indicating when the transmitter is not inducing a proper signal on the loop. - View Dependent Claims (9, 10)
- a transmitter having means for attachment thereof to the designated person or object;
Specification