×

Electronic locating system for persons receiving telephone calls

  • US 4,649,385 A
  • Filed: 07/26/1983
  • Issued: 03/10/1987
  • Est. Priority Date: 08/13/1982
  • Status: Expired due to Fees
First Claim
Patent Images

1. The method of determining the present location of a member of a defined class of individual units the present location of which is not known from among a large population of individual units, each programmed to respond to a predetermined inquiry signal, which are normally distributed throughout a defined facility comprising the steps of:

  • receiving at a central station a request to establish the present location of one of said individual units;

    establishing a two-way communication channel between said central station and a plurality of spaced relay stations, each relay station including a transmitter and a receiver and said relay stations being located so as to be cumulatively capable of substantially covering said facility with infrared energy;

    communicating by a message coded for selecting said one individual unit over said channel with said plurality of relay stations;

    causing said relay stations to transmit an inquiry signal by said infrared energy and enabling the receiver of said one or more relay stations for a predetermined time period following each such transmission;

    receiving the inquiry signal at each of said individual units that is located within the coverage of said one or more relay stations;

    transmitting a radiant energy acknowledgment signal from any individual unit which recognizes the inquiry signal received from a relay station to be the coded message to which it is programmed to respond;

    receiving said acknowledgment signal at any of said relay stations within range of the radiant energy acknowledgment signal transmission;

    transitting to said central station over said channel from any relay station which receives said acknowledgment signal an identification signal which identifies that relay station; and

    utilizing at said central station any identification signal received from a relay station to determine the location of said relay station and hence the approximate location of the individual unit which transmitted said acknowledgment signal, said utilizing including, if more than one identification signal is received, repeating transmission of said inquiry signal at reduced signal level by any relay stations which responds with an identification signal to identify the relay station responsive to the lowest signal level.

View all claims
  • 1 Assignment
Timeline View
Assignment View
    ×
    ×