A METHOD, A DEVICE AND A SYSTEM FOR PREVENTING FALSE ALARMS IN A THEFT-PREVENTING SYSTEM

• US 20110074581A1
• Filed: 04/11/2008
• Published: 03/31/2011
• Est. Priority Date: 04/13/2007
• Status: Active Grant

• Current Assignee: Checkpoint Systems Espana SLU
• Original Assignee: Alert Metalguard APS
• Inventors: Sorensen, Soren, Falkenberg, Verner
• Granted Patent: US 8,754,771 B2
• Time in Patent Office: Days
• US Class Current: 340/568.1
• CPC Class Codes: G08B 13/2402 Electronic Article Surveillance [EAS], i.e. systems using tags for detecting removal of a tagged item from a secure area, e.g. tags for detecting shoplifting mechanical aspects of the tags, e.g. related to locking E05B73/0017; RFID readers G06K7/00; RFID tags G06K19/00; access control systems G07C9/00; anti-theft control in point of sale systems G07G3/003; security seals G09F3/03
• CPC Class Codes: G08B 29/046 prevention of tampering with detection circuits

Abstract

The invention relates to a method, a device and a system for preventing false alarms in a theft-preventing system comprising a magnetic field for detecting at least one metal object in a first detection zone and means for determining a time-difference; said method comprising the steps of detecting a first change in a parameter indicative of the magnetic field in said first detection zone; detecting a second change in the parameter indicative of the magnetic field in said first detection zone; determining a time-difference between the detection of said first change in said parameter and the detection of said second change in said parameter; and performing an action based on said time-difference. In this way, false alarms due to a metal detector falsely detecting for example movement of metal-doors in a first detection zone may be reduced/eliminated. Additionally, the false alarms due to an opening and/or closing of a door with metal parts acting as an active tag may be reduced/eliminated.

Claims

1. A method of preventing false alarms in a theft-preventing system comprising a magnetic field for detecting at least one metal object in a first detection zone and means for determining a time-difference;

said method comprising the steps of

detecting a first change in a parameter indicative of the magnetic field in said first detection zone;

detecting a second change in the parameter indicative of the magnetic field in said first detection zone;

determining a time-difference between the detection of said first change in said parameter and the detection of said second change in said parameter;

performing an action based on said time-difference.

2. A method according to claim 1, wherein the step of detecting a first change in a parameter indicative of the magnetic field in said first detection zone comprises detecting a decrease in the parameter.

3. A method according to claim 1, wherein the step of detecting a second change in the parameter indicative of the magnetic field in said first detection zone comprises detecting an increase in the parameter.

4. A method according to claim 1, wherein the parameter is chosen from the group consisting of

amplitude of the magnetic field;

and

phase of the magnetic field.

5. A method according to claim 1, wherein the step of performing an action based on said time-difference comprises

performing a first action if said time-difference is above a first value;

and

performing a second action if said time-difference is below or equal to said first value.

6. A method according to claim 5, wherein the second action is chosen from the group consisting of

sounding an alarm;

transmitting a silent alarm to e.g. a pager;

setting off a visual alarm; and

transmitting a signal to a video-surveillance system indicating to the video-surveillance system to start monitoring.

7. A method according to claim 5, wherein the first action comprises refraining from sounding an alarm.

8. A method according to claim 5, wherein the first value is chosen from the group consisting of

substantially a second;

and

in the interval 0.5 seconds to 3 seconds.

9. A method according to claim 1, wherein the theft-preventing system further comprises a tag-based theft-preventing system for detecting a tagged object in a second detection zone.

10. A method according to claim 9, wherein the tag-based system is chosen from the group consisting of

resonance circuit system;

RFID system; and

Diode system.

11. A method according to claim 9, wherein the overlap between said first detection zone and said second detection zone is chosen from the group of

coinciding;

disjoint; and

partially overlapping.

12. A device for preventing false alarms in a theft-preventing system comprising a magnetic field for detecting at least one metal object in a first detection zone;

said device comprising

means for detecting a first change in a parameter indicative of the magnetic field in said first detection zone;

means for detecting a second change in the parameter indicative of the magnetic field in said first detection zone;

means for determining a time-difference between the detection of said first change in said parameter and the detection of said second change in said parameter;

means for performing an action based on said time-difference.

13. A device according to claim 12, wherein the means for detecting a first change in a parameter indicative of the magnetic field in said first detection zone are adapted to detect a decrease in the parameter.

14. A device according to claim 12, wherein the means for detecting a second change in the parameter indicative of the magnetic field in said first detection zone are adapted to detect an increase in the parameter.

15. A device according to claim 12, wherein the parameter indicative of the magnetic field is chosen from the group consisting of

an amplitude of the magnetic field;

and

a phase of the magnetic field.

16. A device according to claim 12, wherein the means for performing an action based on said time-difference are adapted to

perform a first action if said time-difference is above a first value;

and

perform a second action if said time-difference is below or equal to said first value.

17. A device according to claim 16, wherein the second action is chosen from the group consisting of

sounding an alarm;

transmitting a silent alarm to e.g. a pager;

setting off a visual alarm; and

transmitting a signal to a video-surveillance system indicating to the video-surveillance system to start monitoring.

18. A device according to claim 16, wherein the first action comprises refraining from sounding an alarm.

19. A device according to claim 16, wherein the first value is chosen from the group consisting of

substantially a second;

and

in the interval 0.5 seconds to 3 seconds.

20. A device according to claim 12, wherein the theft-preventing system further comprises a tag-based system for detecting a tagged object in a second detection zone.

21. A device according to claim 20, wherein the tag-based system is chosen from the group consisting of

resonance circuit system;

RFID system; and

Diode system.

22. A device according to claim 20, wherein the overlap between said first detection zone and said second detection zone is chosen from the group of

coinciding;

disjoint; and

partially overlapping.

23. A system for preventing false alarms in a theft-preventing system, the system comprising a tag-based theft-preventing device, a clock and a metal detector, wherein the system is configured to refrain from sounding an alarm IF the system determines that

the tag-based theft-preventing device indicates the detection of a tagged object substantially at the same time as

the metal detector indicates a change in a metal detector provided magnetic field parameter indicative of an opening and/or closing of a door.