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
Integrated disk driving module including a stepping motor integrally formed with a base unit
Pyridyldiamido transition metal complexes, production and use thereof
Watch dial
Data security for dynamic random access memory using body bias to clear data at power-up
Image output method and device, and image display
Portable gaming device and gaming system combining both physical and virtual play elements
Amnion-derived cells, methods of making and uses thereof
  Randomly Featured Patents
Computerized method and system for maturity assessment of business processes
Wear leveling technique for storage devices
Lamp holder
Semiconductor device and its manufacturing method
Semiconductor chip having a reduced band offset in its p-doped region and method for producing the semiconductor chip
Media cable
Turning tool, and a basic body and a shim plate for a turning tool
Custom fit cap
1,5-dihydro-pyrazolo[34-D]-pyrimidinone derivatives
Storage member