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
Power consumption management in a MIMO transceiver and method for use therewith
Optical signal output apparatus, electrical signal output apparatus, and test apparatus
Automatic fixup of network configuration on system image move
Surface emitting laser device, surface emitting laser array, optical scanning device, and image forming apparatus
Utilizing virtually stored media snapshots for rasterizing print jobs
Systems and methods for advertising on content-screened web pages
Connector with shielding device and method for manufacturing connector
  Randomly Featured Patents
Particulate-free epitaxial process
Fault analysis apparatus, fault analysis method, and recording medium
Closure clip for gable-top carton
Color separation and synthesis systems, color separation systems and color synthesis systems, illumination optical systems, projection optical systems, and projection display devices using the
Method of simultaneous display of two pictures for internet-functional television receiver
Electrical connector
Shift and throttle management during cruise control
Guiding apparatus for the travel elements of endless conveyors, such as escalators and the like
Computer front bezel
Fuel rod spacer with perimeter scoops for diverting liquid coolant flow