Patent ID: 8904708

Claim:
Apparatus for detecting an object in an area adjacent a doorway, the apparatus comprising: a plurality of transducers mounted proximate the doorway, wherein at least two of the transducers are positioned to repeatedly transmit signals toward an area adjacent the doorway, and wherein at least two of the transducers are positioned to repeatedly receive return signals from a transmitting transducer; and a processor operably connected to the plurality of transducers for detecting, in the area adjacent the doorway, an object by determining the object's position and the object's movement, wherein the processor is configured to measure times of flight between transmission of signals and reception of corresponding return signals and to calculate a corresponding determined distance from the corresponding transducer to the object based on a corresponding time of flight and to derive a corresponding spherical surface with a location of a corresponding transceiver as a center of the spherical surface and the corresponding determined distance as a radius of the spherical surface and to determine the object's position by determining coordinates of an intersection of at least two corresponding spherical surfaces; wherein the processor is configured to determine the object's movement based upon transmission of signals and Doppler shift in the reception of corresponding return signals.