Security system

• US 5,374,936 A
• Filed: 02/28/1994
• Issued: 12/20/1994
• Est. Priority Date: 02/28/1994
• Status: Expired due to Term

• Current Assignee: Trakover, LLC
• Original Assignee: Jun Feng
• Inventors: Feng, Jun
• Primary Examiner(s): Blum, Theodore M.
• Application Number:
  US08/202,504
• Time in Patent Office: 295 Days
• Field of Search: 342/457, 342/463, 342/353, 455/13.1, 455/53.1, 455/54.1, 340/539
• US Class Current: 342/457
• CPC Class Codes: G01S 5/06 Position of source determined by co-ordinating a plurality of position lines defined by path-difference measurements G01S5/12 takes precedence
• CPC Class Codes: G08B 25/009 Signalling of the alarm condition to a substation whose identity is signalled to a central station, e.g. relaying alarm signals in order to extend communication range

Abstract

A security system provides accurate positioning, in a two or three dimensional coordinate system, of an alarm signal transmitter which emits an alarm signal upon activation by a user. The security system includes at least three relay stations, at least one portable signal transmitter, and a central station. The alarm signal from the signal transmitter is received by the relay stations at different time intervals or with different intensities. The time or intensity data are then sent to the central station for processing, wherein the coordinates of the signal transmitter are quickly determined by solving a set of equations based on these data. The accuracy of the coordinates of the signal transmitter depends on accuracy of the measured time or intensity data.

Claims

1. A security system, comprising:

at least one portable signal transmitter responsive to a user input for emitting an alarm signal including an identification code that identifies said at least one portable signal transmitter;

at least three relay stations positioned at predetermined locations, each relay station comprising,

a receiver for receiving said alarm signal and a calibration signal,

a timer responsive to said receiver for measuring a time interval between receipt of said alarm signal and said calibration signal by said receiver, and

a transmitter responsive to said timer for transmitting a data signal including said time interval, said signal transmitter identification code and a relay station identification code; and

a central station positioned in a predetermined location, said central station comprising,

a receiver for receiving said data signal from each of said relay stations and said alarm signal from said alarm signal transmitter,

a transmitter responsive to said receiver for transmitting said calibration signal, and

a data processor having memory resident instructions for processing said data signal to calculate coordinates of said signal transmitter.

2. The security system of claim 1, wherein said transmitter of said central station transmits said calibration signal periodically.

3. The security system of claim 1, wherein said transmitter of said central station transmits;

said calibration signal upon receipt of said alarm signal.

4. The security system of claim 1, wherein said timer of each of said at least three relay stations is synchronized by a synchronizing signal from said central station.

5. A security system, comprising:

at least one portable signal transmitter responsive to a user input for emitting a first alarm signal including an identification code that identifies said at least one portable signal transmitter;

at least three relay stations positioned in predetermined locations, each relay station comprising,

a receiver for receiving said first alarm signal and a first calibration signal, and

a transmitter responsive to said receiver for transmitting a second alarm signal including a first alarm signal identification code and a relay station identification code upon receipt of said first alarm signal by said receiver and for transmitting a second calibration signal including a first calibration signal identification code and said relay station identification code upon receipt of said first calibration signal; and

a central station positioned in a predetermined location, comprising

a receiver for receiving said first alarm signal, and said second calibration signal and said second alarm signal from each of said relay stations,

a timer for measuring a time interval between said second alarm signal and said second calibration signal for each of said relay stations,

a transmitter responsive to said receiver for transmitting a first calibration signal, and

a data processor having memory resident instructions for processing data including said time interval for each of said relay stations to calculate coordinates of said the signal transmitter.

6. The security system of claim 5, wherein said transmitter of said central station transmits said first calibration signal periodically.

7. The security system of claim 5, wherein said transmitter of said central station transmits said first calibration signal upon receipt of said first alarm signal.

8. A security system, comprising:

at least one portable signal transmitter responsive to a user input for emitting an alarm signal including an identification code that identifies said portable signal transmitter;

at least three relay stations positioned at predetermined locations, each relay station comprising,

a receiver for receiving said alarm signal and a calibration signal,

an intensity meter responsive to said receiver for measuring a signal strength of said alarm signal and a calibration signal, and

a transmitter responsive to said intensity meter for transmitting a data signal including said signal strength of said alarm signal, signal strength of said calibration signal, a relay station identification code, and signal transmitter identification code; and

a central station positioned in a predetermined location, said central station comprising,

a receiver for receiving said data signal from each of said relay stations and said alarm signal from said alarm signal transmitter,

a transmitter responsive to said receiver for transmitting said calibration signal, and

a data processor having memory resident instructions for processing said data signal to calculate coordinates of said signal transmitter.

9. The security system of claim 8, wherein said transmitter of said central station transmits said calibration signal periodically.

10. The security system of claim 8, wherein said transmitter of said central station transmits said calibration signal upon receipt of said alarm signal.