초록 ▼

An improvement in Instrusion Alarms of the type wherein a field wire acts as a transmitting antenna to produce an electric field and wherein a sense antenna is placed in the vicinity of the field wire to detect an intruder wherein at least one pair of field wires are employed at the extremities of a

An improvement in Instrusion Alarms of the type wherein a field wire acts as a transmitting antenna to produce an electric field and wherein a sense antenna is placed in the vicinity of the field wire to detect an intruder wherein at least one pair of field wires are employed at the extremities of a vertical configuration with sense wires between the field wires. The movement of a large object in the vicinity of such a system produces an equal perturbation on both of the sense wires so that no alarm is set off while an actual intrusion will cause a difference which is detected and utilized to provide an alarm system which is less susceptible to false alarms than the usual alarm systems.

대표청구항 ▼

In an intruder alarm system wherein a field wire creates an electric field and a sense wire is provided parallel to said field wire and wherein a sensitive amplifying and filtering circuit detects perturbations on said sense wire resulting from the presence of an intruder intersecting the field betw

In an intruder alarm system wherein a field wire creates an electric field and a sense wire is provided parallel to said field wire and wherein a sensitive amplifying and filtering circuit detects perturbations on said sense wire resulting from the presence of an intruder intersecting the field between the field wire and the sense wire, the improvement comprising: a. at least two field wires, said field wires being spaced from each other and running generally parallel to each other; b. sense wires between said field wires for sensing the field created between each sense wire and each field wire, there being at least two sense wires, said sense wires being spaced from corresponding field wires whereby a common disturbance creates equal voltages on said sense wires, said sense wires being connected to a balanced circuit having an input leading to a filtering and detection system whereby equal voltages on said sense wires will counteract each other and said detection system is actuated only by unequal voltages developed in said two sense wires and; c. said field and sense wires being arranged in a substantially vertical array.