Monitored security switch assembly

• US 5,821,870 A
• Filed: 04/28/1997
• Issued: 10/13/1998
• Est. Priority Date: 05/08/1996
• Status: Expired due to Fees

• Current Assignee: Jackson Research, Inc.
• Original Assignee: Jackson Research, Inc.
• Inventors: Jackson, John T. Jr.
• Primary Examiner(s): Hofsass, Jeffery A.
• Assistant Examiner(s): Lee, Benjamin C.
• Application Number:
  US08/845,866
• Time in Patent Office: 533 Days
• Field of Search: 340/541, 340/568, 340/571, 340/687, 340/652, 340/686
• US Class Current: 340/687
• CPC Class Codes: G01R 31/11 using pulse reflection methods
• CPC Class Codes: G08B 29/06 Monitoring of the line circuits, e.g. signalling of line faults

Abstract

A monitored security switch assembly includes a switching system, a transmission line, and a monitoring system. The switching system has a load element. The security switch assembly uses an oscillatory voltage to determine if the monitoring system, the switching system and the transmission line are impedance matched. The security switch system can function in a transmission mode or a reflection mode.

Claims

1. A monitored security switch assembly, comprising:

a switching system including a first impedance, the switching system responsive to a security condition of an object to be protected to switchably alter the value of the first impedance;

a transmission line, the switching system being impedance matched with the transmission line; and

a monitoring system which provides at least one oscillatory voltage to the switching system through the transmission line, the monitoring system detecting an impedance mismatch between the switching system and the transmission line due to the security condition, or tampering or cutting of the transmission line.

2. The monitored security switch assembly according to claim 1, wherein the at least one oscillatory voltage includes a radio frequency oscillatory voltage.

3. The monitored security switch assembly according to claim 1, wherein the monitoring system includes an oscillator and a mismatch detector.

4. The monitored security switch assembly according to claim 1, wherein the monitoring system includes a voltage controlled oscillator and a mismatch detector.

5. The monitored security switch assembly according to claim 1, wherein the monitoring system includes a network analyzer.

6. The monitored security switch assembly according to claim 1, wherein the monitoring system determines whether a reflected oscillatory voltage is received from the switching system.

7. The monitored security assembly according to claim 1, wherein the switching system includes a tamper switch, and the monitoring system includes a continuity detector to provide a direct current voltage to the tamper switch.

8. The monitored security switch assembly according to claim 1, wherein the monitoring system includes a continuity detector to provide a direct current voltage to the switching system, the continuity detector detecting an interruption of the direct current voltage.

9. The monitored security switch assembly according to claim 1, wherein the switching system includes a tamper switch, and the oscillatory voltage being provided through the tamper switch.

10. The monitored security switch assembly according to claim 1, wherein the switching system further includes a bandpass filter, wherein the monitoring system provides at least two oscillatory voltages, at least one of the oscillatory voltages having a frequency within a pass band of the bandpass filter.

11. The monitored security switch assembly according to claim 10, wherein the at least one oscillatory voltage includes a radio frequency oscillatory voltage.

12. The monitored security switch assembly according to claim 11, wherein the monitoring system includes an oscillator and a mismatch detector.

13. The monitored security switch assembly according to claim 12, wherein the oscillator is a voltage controlled oscillator.

14. The monitored security switch assembly according to claim 13, wherein the monitoring system determines whether a reflected oscillatory voltage is received from the switching system.

15. The monitored security switch assembly according to claim 14, wherein the switching system includes a tamper switch, and the monitoring system includes a continuity detector to provide a direct current voltage to the tamper switch.

16. A monitored security switch assembly, comprising:

a transmission line;

a switching system coupled to the transmission line and including an oscillator which provides at least one oscillatory voltage for transmission over the transmission line, the switching system responsive to a security condition of an object to be protected to disconnect the at least one oscillatory voltage from the transmission line; and

a monitoring system which receives and detects the at least one oscillatory voltage from the switching system through the transmission line, wherein the monitoring system is impedance matched with the transmission line, the monitoring system monitoring whether the monitoring system and the transmission line are impedance matched due to the security condition or to detect tampering or cutting of the transmission line.

17. The monitored security switch assembly according to claim 16, wherein the at least one oscillatory voltage includes a radio frequency oscillatory voltage.

18. The monitored security switch assembly according to claim 16, wherein the oscillator includes a voltage controlled oscillator.

19. The monitored security switch assembly according to claim 16, wherein the monitoring system determines whether a voltage standing wave ratio is changed.

20. The monitored security switch assembly according to claim 16, wherein the monitoring system includes a continuity detector for providing a direct current voltage to the switching system and detecting an interruption of the direct current voltage.

21. The monitored security switch assembly according to claim 16, wherein the monitoring system provides a direct current voltage to the switching system.

22. The monitored security switch assembly according to claim 21, wherein the switching system includes decoupling elements to decouple the oscillatory voltage and the direct current voltage.

23. The monitored security switch assembly according to claim 22, wherein the decoupling elements include a capacitor and a choke.

24. The monitored security switch assembly according to claim 23, wherein the at least one oscillatory voltage includes a radio frequency oscillatory voltage.

25. The monitored security switch assembly according to claim 24, wherein the oscillator includes a voltage controlled oscillator.

26. A monitoring system for a security switch assembly, comprising:

an oscillator for providing an oscillatory voltage to a transmission line and a switching system having a first impedance, wherein the switching system is responsive to a security condition of an object to be protected to switchably alter the first impedance, and wherein the transmission line is impedance matched with each of the oscillator and the switching system; and

a mismatch detector connected to the transmission line and impedance matched with the transmission line, wherein the mismatch detector detects whether an impedance mismatch occurs due to the security condition, or tampering or cutting of the transmission line.

27. The monitoring system according to claim 26, wherein the oscillatory voltage includes a radio frequency oscillatory voltage.

28. The monitoring system according to claim 27, wherein the oscillator is a voltage controlled oscillator.

29. The monitoring system according to claim 28, wherein the mismatch detector determines whether a reflected oscillatory voltage is received from the transmission line.

30. The monitoring system according to claim 28, wherein the mismatch detector determines whether a voltage standing wave ratio is changed.