Resources Contact Us Home
Browse by: INVENTOR PATENT HOLDER PATENT NUMBER DATE
 
 
Intrusion detection method and apparatus










Image Number 2 for United States Patent #4229811.

An improved method and apparatus for carrying the method are disclosed which provide for selection by the user of a surface used as a reference in the detection of an intrusion. This is achieved by periodically projecting pulses of acoustical energy from a source towards a reference surface and detecting the reflection of such pulses of acoustical energy at a receiver and providing a first indication or signal representative of the reflected pulses. A second indication or signal is generated which is adjustable and representative of the time elapsed between the projection of a pulse of acoustical energy from the source and the reception at the receiver of the pulse of acoustical energy when reflected from the selected reference surface. The variations between the first and second indications are detected and compared and an alarm is generated when a variation is detected in the indications. In the embodiment disclosed, the absence of variations between the first and second indications is measured by the coincidence of the first and second indications.








 
 
  Recently Added Patents
Enediyne compounds, conjugates thereof, and uses and methods therefor
Metal foil laminate, substrate for mounting LED, and light source device
Controller for machine tool and five-axis simultaneous control machine tool controlled thereby
Gateway channel utilization
Nut
Signal conversion control circuit for touch screen and method thereof
Process and apparatus for producing composite material that includes carbon nanotubes
  Randomly Featured Patents
Self-propelled working vehicle
Lens sheet and producing method therefor
Multiple field entry telephone directory for a cellular telephone
Screw with deployable interlaced dual rods
Friendly fire archery bow
Card-shaped data carrier
Steam condensate corrosion inhibitor compositions and methods
Optical measurement module for measuring angles and/or distances
Heat reclamation apparatus
Method for epitaxial growth of thin semiconductor layer from solution