Fault monitoring event detection device

DETAILED DESCRIPTION OF THE DRAWINGS Referring now to FIG.
1, the detection device comprises a passive infrared sensor 1 and a microwave sensor 2 which are connected to a microcontroller/microprocessor control function 5.
Outputs from the microcontroller 5 are connected to an alarm output activator 3 and a fault indicator 4.
Referring to FIG.
2, which is a functional diagram of the microcontroller of FIG.
1, it can be seen that the inputs from the passive infrared sensor and the microwave sensor are connected to a logic "and" function 6 whose output is connected to the alarm output activator 3.
The outputs from the passive infrared sensor 1 and the microwave sensor 2 are also connected to a signal detector 7 which in turn is connected to counters A and B.
The signal detector can increment counters A and B in response respectively to signals from the passive infrared sensor 1 and the microwave sensor 2 and can also reset the counters to zero.
The signal detector operates in such a fashion that if it applies an increment to counter A it will automatically reset counter B to zero and vice versa.
Outputs from counters A and B are led to a logic "or" function B which in turn is connected to the fault indicator 4.
The detection device is shown with two sensing means each having an associated counter, but of course if more than two sensing means and more than two counters are used, then the signal detector automatically resets all counters other than the incremented counter to zero.
The counters A and B are set to give an output when a pre-determined threshold level, for example one million, is reached.
When the number of input signals counted by either counter A or counter B exceeds the threshold level an output signal indicating a fault condition is generated.
The output of the fault indicator may be connected to a sounder, a visual display, or a telecommunications device.
The sequence of operations of the fault monitoring system is illustrated in the fault monitoring microcontroller algorithm of FIG