Security system

• US 5,691,697 A
• Filed: 09/22/1995
• Issued: 11/25/1997
• Est. Priority Date: 09/22/1995
• Status: Expired due to Fees

• Current Assignee: Kidde Technologies, Inc. (Raytheon Technologies Corporation d/b/a RTX)
• Original Assignee: Kidde Technologies, Inc. (Raytheon Technologies Corporation d/b/a RTX)
• Inventors: Hallee, Donald O., Osborne, John P., Carvalho, Carlos E.
• Primary Examiner(s): SWANN III, GLEN R
• Application Number:
  US08/532,351
• Time in Patent Office: 795 Days
• Field of Search: 340/544, 340/426, 340/945
• US Class Current: 340/544
• CPC Class Codes: G08B 13/20 Actuation by change of fluid pressure
• CPC Class Codes: G08B 25/14 Central alarm receiver or annunciator arrangements
• CPC Class Codes: G08B 29/185 Signal analysis techniques for reducing or preventing false alarms or for enhancing the reliability of the system

Abstract

A security system includes a pressure sensing circuit for generating an electrical signal in response to changes in pressure and a signal processing circuit, connected to receive the electrical signal, for determining whether the electrical signal represents an intrusion pattern. A pressure sensing circuit generates an electrical signal in response to changes in pressure and a trigger circuit for determining whether an intrusion has occurred by determining whether a peak of the electrical signal has an amplitude that exceeds a floating amplitude threshold, wherein the floating amplitude threshold compensates for ambient noise in the enclosed area. A monitor mode measures intrusion data in a specific enclosed area and determines security system thresholds in accordance with the measured intrusion data.

Claims

1. A security system comprising:

a pressure sensing circuit for generating an electrical signal in response to changes in pressure; and

a signal processing circuit, connected to receive the electrical signal, for determining whether the electrical signal represents an intrusion pattern,

wherein the electrical signal comprises an analog signal,

wherein the signal processing circuit samples the analog signal and determines whether the samples represent the intrusion pattern.

2. The security system of claim 1, further comprising:

a notification circuit, connected to the signal processing circuit, for providing an external alarm notification when the signal processing circuit determines that the electrical signal represents the intrusion pattern.

3. The security system of claim 1, further comprising:

an event logging circuit, connected to the signal processing circuit, for writing event data to an event log in a memory connected to the signal processing circuit.

4. The security system of claim 3, wherein the event logging circuit writes event data to the event log when the signal processing circuit determines that the electrical signal represents the intrusion pattern.

5. The security system of claim 1, wherein the signal processing circuitry includes:

a digital signal processing circuit.

6. The security system of claim 1, wherein the signal processing circuit includes:

condition detection circuitry for determining whether the electrical signal meets at least one predetermined condition which represents the intrusion pattern.

7. The security system of claim 6, wherein the predetermined condition requires that a maximum intrusion peak amplitude of the electrical signal occur within a pulse width time period in which the electrical signal exceeds a pressure threshold value.

8. The security system of claim 6, wherein the predetermined condition requires that a pulse width time period, in which the electrical signal exceeds a pressure threshold value, be within a preset time range.

9. The security system of claim 6, wherein the predetermined condition requires that a difference between a maximum intrusion peak amplitude and a minimum intrusion peak amplitude be greater than an intrusion pressure threshold.

10. The security system of claim 6, wherein the predetermined condition requires that a difference between a maximum recovery peak amplitude and a minimum intrusion peak amplitude be greater than a recovery threshold.

11. The security system of claim 6, wherein the predetermined condition requires that a pulse width time period, in which the electrical signal exceeds a pressure threshold value, be greater than a preset time threshold.

12. The security system of claim 6, wherein the predetermined condition requires that an increase in the electrical signal be greater than a predetermined rate.

13. The security system of claim 1, wherein the pressure sensing circuit includes:

a temperature compensation circuit, connected to receive the electrical signal, for compensating for changes in the response of the pressure sensing circuit due to temperature.

14. The security system of claim 1, wherein the pressure sensing circuit includes:

a frequency compensation circuit, connected to receive the electrical signal, for conditioning the frequency response of the electrical signal.

15. The security system of claim 14, wherein the frequency compensation circuit conditions the electrical signal to provide a flat frequency response.

16. The security system of claim 1, wherein the pressure sensing circuit includes:

an amplifier for amplifying the electrical signal; and

an adjustable gain calibration circuit for setting the gain of the amplifier in accordance with a calibration value.

17. The security system of claim 16, wherein the calibration value is selected by a user and down-loaded to the adjustable gain calibration circuit by the signal processing circuit.

18. The security system of claim 1, wherein the pressure sensing circuit includes:

an adjustable μ

bar range select circuit, connected to receive the electrical signal, for amplifying the electrical signal in accordance with a pressure threshold value.

19. The security system of claim 18, wherein the pressure threshold value is selected by a user and down-loaded to the adjustable μ

bar range select circuit.

20. The security system of claim 1, wherein the signal processing circuit further determines whether the electrical signal represents another intrusion pattern.

21. The security system of claim 1, wherein the signal processing circuit determines whether the electrical signal represents the intrusion pattern by comparing the electrical signal to a set of predetermined thresholds.

22. The security system of claim 21, wherein the set of predetermined thresholds are specific to an enclosed area within which the security system is to be used.

23. The security system of claim 22, wherein the enclosed area is an aircraft.

24. The security system of claim 21, wherein the set of predetermined thresholds are established by a user prior to arming the system.

25. The security system of claim 24, wherein the set of thresholds are in accordance with a user selected aircraft type.

26. The security system of claim 24, wherein the set of thresholds includes a pressure threshold P_TH, a minimum pulse width threshold t_min, and a evaluation period t_max.

27. The security system of claim 1, further comprising:

a display device, and

a entry/exit button, connected to the signal processing circuit, for displaying, on the display device, available preset system thresholds.

28. The security system of claim 27, further comprising:

a select button, connected to the signal processing circuit, for selecting particular preset available thresholds.

29. The security system of claim 28, wherein the entry/exit button further causes display of a menu for modification of system thresholds and wherein the select button selects modified system thresholds.

30. The security system of claim 29, wherein the menu includes an event menu for displaying, erasing, or dumping an event log.

31. The security system of claim 29, wherein the menu includes a monitor menu item for detecting intrusions into an enclosed area and for measuring intrusion data associated with the intrusions, wherein the signal processing circuit determines the set of system thresholds from the measured intrusion data.

32. The security system of claim 1, wherein the security system is portable.

33. The security system of claim 1, wherein the pressure sensing circuit comprises an air pressure sensing circuit.

34. A security system comprising:

a pressure sensing circuit for generating an electrical signal in response to changes in pressure; and

a signal processing circuit, connected to receive the electrical signal, for determining whether the electrical signal represents an intrusion pattern, further comprising;

a trigger circuit, connected to receive the electrical signal, for determining whether the electrical signal represents a possible intrusion and for waking up the signal processing circuit, when the electrical signal represents a possible intrusion, to initiate the signal processing circuit'"'"'s determination as to whether the electrical signal represents the intrusion pattern.

35. The security system of claim 34, wherein the trigger circuit determines whether a peak of the electrical signal has an amplitude that exceeds an amplitude threshold.

36. The security system of claim 35, wherein the amplitude threshold is a floating amplitude threshold that compensates for ambient noise.

37. The security system of claim 35, wherein the trigger circuit determines whether a peak of the electrical signal has a pulse width that exceeds a pulse width threshold.

38. The security system of claim 34, wherein the pressure sensing circuit includes:

an amplifier for amplifying the electrical signal; and

an adjustable gain calibration circuit for setting the gain of the amplifier in accordance with a calibration value.

39. The security system of claim 38, wherein the calibration value is down-loaded to the adjustable gain calibration circuit by the signal processing circuit.

40. The security system of claim 34, wherein the pressure sensing circuit includes:

an adjustable μ

bar range select circuit, connected to receive the electrical signal, for amplifying the electrical signal in accordance with a pressure threshold value.

41. The security system of claim 40, wherein the pressure threshold value is selected by a user and down-loaded to the adjustable μ

bar range select circuit.

42. A method of detecting intrusions comprising:

sensing changes in pressure;

generating an electrical signal in response to the sensed changes in pressure; and

determining whether the electrical signal represents an intrusion pattern,

wherein the electrical signal comprises an analog signal,

wherein said determining includes sampling the analog signal by a signal processing circuit that determines whether the samples represent the intrusion pattern.

43. A method of determining security system thresholds, comprising:

providing a security system for detecting changes in air pressure to detect intrusions into enclosed areas, wherein the security system includes a monitor mode for measuring intrusion data in specific enclosed areas and for determining security system thresholds in accordance with the measured intrusion data.

44. The method of claim 43, further comprising:

placing the security system in a specific enclosed area; and

selecting the monitor mode of the security system.

45. The method of claim 44, further comprising:

intruding into the specific enclosed area;

detecting the intrusion; and

measuring intrusion data associated with the intrusion.

46. The method of claim 45, further comprising:

determining the security system thresholds from the measured intrusion data.