Automatically adjustable and self-testing dual technology intrusion detection system for minimizing false alarms

• US 5,331,308 A
• Filed: 07/30/1992
• Issued: 07/19/1994
• Est. Priority Date: 07/30/1992
• Status: Expired due to Term

• Current Assignee: Napco Security Systems Incorporated
• Original Assignee: Napco Security Systems Incorporated
• Inventors: Kolb, Lawrence M., Buccola, Charles S.
• Primary Examiner(s): Swann, III, Glen R.
• Application Number:
  US07/923,103
• Time in Patent Office: 719 Days
• Field of Search: 340/522, 340/554, 340/567
• US Class Current: 340/522
• CPC Class Codes: G08B 13/2494 by interference with electro-magnetic field distribution combined with other electrical sensor means, e.g. microwave detectors combined with other sensor means

Abstract

A dual sensor intrusion detection system utilizes adaptive sensor detection techniques to reduce false alarms. The adaptive sensor detection techniques include increasing the stability of one sensor after the other sensor continuously detects motion without confirmation by the first sensor

Claims

1. An intrusion detection system which comprises:

dual sensing means for monitoring motion within a predetermined volume of space, said dual sensing means having a first sensor for detecting motion within said volume of space and a second sensor for verifying said motion detected by said first sensor so as to activate an alarm; and

processing means interactive with said dual sensing means, such that said processing means increases the stability of said second sensor when said first sensor detects motion for a first predetermined period of time without verification by said second sensor, said stability defining when said second sensor activates said alarm.

2. The system according to claim 1, wherein one of said first and second sensors is an active sensor and the other sensor is a passive sensor.

3. The system according to claim 1, wherein said processing means modifies the sensitivity of said first sensor when said first sensor detects a predetermined number of disturbances.

4. The system according to claim 3, wherein said processing means modifies the sensitivity of said first sensor a number of times until said first sensor is in a predetermined maximum stability mode.

5. An intrusion detection system which comprises:

first detecting means for monitoring motion within a predetermined volume of space and for generating a first detect signal in response to detection of motion in said predetermined volume of space;

second detecting means for generating a second detect signal in response to detection of said motion in said predetermined volume of space; and

processing means for receiving said first and second detect signals, for activating said second detecting means in response to first detect signal, for modifying the number of said second detect signals required to activate an alarm when said first detecting means detects motion for a predetermined period of time without verification by said second detecting means and for activating said alarm when said modified number of said second detect signal is received by said processing means.

6. The system according to claim 5, further comprising means for multiplexing said first and second detect signals such that said processing means selectively receives said first detect signal and said second detect signal.

7. The system according to claim 5, wherein said processing means modifies the number of said second detect signals by increasing a pulse count and a timing window associated with said second detect signal.

8. The system according to claim 7, wherein said pulse count and said timing window are modified between a normal detection mode and a high stability detection mode.

9. The system according to claim 8, wherein said normal detection mode comprises a pulse count of two pulses and a timing window of five seconds.

10. The system according to claim 8, wherein said high stability detection mode comprises a pulse count of four pulses and a timing window of ten seconds.

11. The system according to claim 8, further comprising means for self-testing said first detecting means and said second detecting means.

12. An intrusion detection system which comprises:

microwave detecting means for monitoring motion within a predetermined volume of space and for generating a first detect signal in response to detection of motion in said predetermined volume of space;

PIR detecting means for generating a second detect signal in response to detection of said motion in said predetermined volume of space; and

processing means for receiving said first and second detect signals, for activating said PIR detecting means in response to said first detect signal, for modifying the number of said second detect signals required to activate an alarm when said microwave detecting means detects motion and said PIR detecting means fails to detect motion for a first predetermined period of time, and for activating said alarm when said modified number of said second detect signal is received by said processing means.

13. The system according to claim 12, further comprising means for multiplexing said first and second detect signals such that said processing means selectively receives said first detect signal or said second detect signal.

14. The system according to claim 12, wherein said processing means modifies the number of said second detect signals by increasing a PIR pulse count and a PIR timing window.

15. The system according to claim 14, wherein said PIR pulse count and PIR timing window are modified between a normal detection mode and a high stability detection mode.

16. The system according to claim 15, wherein said normal detection mode comprises a PIR pulse count of two pulses and PIR timing window of five seconds.

17. The system according to claim 15, wherein said high stability detection mode comprises a PIR pulse count of four pulses and a PIR timing window of ten seconds.

18. The system according to claim 14, wherein modifying the number of said second detect signals comprises decreasing said PIR pulse count and said PIR timing window when no motion is detected by said microwave detecting means for a second predetermined period of time.

19. The system according to claim 12, further comprising means for self-testing said microwave detecting means and said PIR detecting means.

20. The system according to claim 19, wherein said self-test means comprises a resistor positioned in close proximity to said PIR detecting means such that heat radiating from said resistor activates said PIR detecting means.

21. The system according to claim 19 wherein said self-test means comprises pulse-width modulating said microwave detecting means.

22. A method for detecting an intruder, comprising:

detecting a first motion detect signal from a first sensor;

verifying said first motion detect signal with a second sensor; and

modifying the stability of said second sensor when said first sensor detects motion without verification by said second sensor for a first predetermined period of time and when said first sensor fails to detect motion for a second predetermined period of time.

23. The method of according to claim 22 further comprising modifying the sensitivity of said first sensor when said first sensor detects motion a predetermined number of times.

24. The method according to claim 23, wherein the sensitivity of said first sensor is modified a number of times until said first sensor is in a predetermined maximum mode.

25. The method according to claim 22, wherein said stability of said second sensor is increased when said first sensor detects motion without verification by said second sensor for said first predetermined period of time.

26. The method according to claim 22, wherein said stability of said second sensor is decreased when said first sensor fails to detect motion for said second predetermined period of time.