Resources Contact Us Home
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
Motorized home appliance door
Computer system and volume migration control method using the same
Method and apparatus for supporting HARQ
Method of stimulating tissue healing
Method and apparatus for selective decoding in a wireless communication system
Solid-state image capture device and image capture apparatus
Vapor phase decarbonylation process
  Randomly Featured Patents
Ceramic shell moulds, manufacture and use
Dynamic flashing reflector rotatably mounted on vehicle wheel
Valve for winterizing a pool
Method and apparatus for storing used tires
3-chloro 1,1,1,6,6,6-hexafluoro-2,4-hexadiene and solvent compositions containing the same
Semi-hard magnetic material for a reed switch and process for producing the same
Active sensor with operating mode changeover
Thermal transfer image-receiving sheets
Goggle strap alignment and fastening guide for motorcycle type helmet
Duplicating system for a lathe