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
Method and CTDevice for computer tomographic spiral scanning of a patient
Differential ring oscillator and method for calibrating the differential ring oscillator
Method and apparatus for power management control of an embedded memory having sleep and shutdown features
Method of manufacturing semiconductor device and semiconductor device
Dispensing of restricted goods
Cache memory control device, semiconductor integrated circuit, and cache memory control method
Debugging using code analysis
  Randomly Featured Patents
Antenna sharing device and wireless communication terminal using the same
Method and device for determining an image shift in an image sequence
Vacuum cleaner with continuous liquid pick-up
Method of producing fine particles of anthraquinone structure-containing pigment, fine particles of anthraquinone structure-containing pigment produced thereby, colored pigment dispersion comp
System and method for using an output transformer for laser diode drivers
Mirror assembly for vehicle
Metal mesh gloves
Process for producing aromatic ring alkylated phenols
Flat field telecentric scanner
Phenylazophenyloxytriazolyl compounds