Fault detection in combination intrusion detection systems
First Claim
1. In an intrusion detection system of the class employing dual technology subsystems, wherein a first subsystem provides a first output signal responsive to the detection of an intruder and wherein a second subsystem provides a second output responsive to the detection of an intruder and including means responsive to said first and second output signals for generating an alarm, the improvements therein comprising;
- first counting means for counting the number of said first output signals provided by said first subsystem and for providing an output signal when said count equals a selected count,second counting means for counting the number of said second output signals provided by said second subsystem and for providing an output signal when said count equals a predetermined count,logic means coupled to said first and second counting means for generating a fault signal indicating a system malfunction for said output signal from said first or second counting means.
2 Assignments
0 Petitions
Accused Products
Abstract
An intrusion detection system employs a microwave subsystem and a passive infra-red subsystem. Both systems must produce an output signal indicative of an intrusion in order for the system to produce an alarm. There is disclosed a supervision circuit which monitors the number of trips of the microwave system as well as the number of trips of the PIR system. If the number of trips which are indicative of false alarms exceeds preset counts then an alarm is produced indicating that there is a failure in the microwave or the PIR system. The system further monitors the microwave system to determine whether the transmit and receiving diodes are functioning properly. The system will also indicate a fault if an intruder or an object is placed within a predetermined protection dome implemented by the system. Hence the system can produce multiple faults indicative of subsystem failures to notify the user of the system that such a failure has occurred.
69 Citations
15 Claims
-
1. In an intrusion detection system of the class employing dual technology subsystems, wherein a first subsystem provides a first output signal responsive to the detection of an intruder and wherein a second subsystem provides a second output responsive to the detection of an intruder and including means responsive to said first and second output signals for generating an alarm, the improvements therein comprising;
-
first counting means for counting the number of said first output signals provided by said first subsystem and for providing an output signal when said count equals a selected count, second counting means for counting the number of said second output signals provided by said second subsystem and for providing an output signal when said count equals a predetermined count, logic means coupled to said first and second counting means for generating a fault signal indicating a system malfunction for said output signal from said first or second counting means. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
-
-
9. In an intrusion detection system employing a microwave subsystem for transmitting a microwave signal and for receiving said signal to determine from said received signal the presence of an intruder according to the Doppler effect and to produce an output signal indicative thereof, and a passive infra-red system (PIR) for receiving infra-red radiation from an intruder and for providing an output signal indicative thereof, said system providing an alarm output for the presence of both output signals, the improvement therewith comprising;
-
first counting means for counting the number of output signals from said microwave subsystem and for providing a first signal when said count equals a selected count, second counting means for counting the number of output pulses from said passive infra-red subsystem and for providing a second signal when said count exceeds a preselected count, first means coupled to said microwave subsystem for monitoring the amplitude of said received signal against threshold signal and for providing a third signal when said received signal exceeds said threshold signal, second means coupled to said microwave subsystem for developing a DC level according to the magnitude of said transmitted signal and for comparing the DC level with a reference level and for providing a fourth output signal when said level falls below said reference level, and gating means responsive to said first, second, third and fourth signals for providing a fault output indicating a system malfunction for the receipt of any one of said signals. - View Dependent Claims (10, 11, 12, 13, 14, 15)
-
Specification