Zone Input Enhancer for Burglar Alarm Noise Immunity
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Solution Overview
Problem
Existing burglar alarm systems are vulnerable to compromise attempts due to their reliance on constant voltage and current, which can be easily manipulated, and are sensitive to low-level electromagnetic noise, making them susceptible to external interference.
Innovation Solution
A zone input enhancer that introduces randomly variable voltage and timing to the zone loop, directly measures current flow, and uses correlation and autocorrelation calculations to detect changes, enhancing the system's immunity to electromagnetic noise and compromising attempts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If constant voltage and current are used in the zone loop, then the system is simple to operate and install, but the system becomes vulnerable to compromise attempts and electromagnetic noise
Solution Approach 1:
The patent applies dynamics by transitioning from constant voltage/current to dynamically varying voltage with random amplitude and timing characteristics. The zone loop power source now provides voltage that continuously changes in amplitude and timing according to a random pattern, making the system adaptive and resistant to static compromise attempts while maintaining operational simplicity through automated generation of the random voltage pattern
Solution Approach 2:
The patent implements parameter changes by modifying the voltage parameters (amplitude, timing, frequency) of the zone loop power source. The voltage amplitude varies randomly within a defined range, and the timing between voltage transitions is randomized, creating a dynamic electrical environment that prevents predictable manipulation while preserving the fundamental voltage-based detection mechanism
2Reliability
If voltage level measurement is used to detect zone status, then the system is easy to implement, but it becomes sensitive to electromagnetic noise
Solution Approach 1:
The patent applies feedback by implementing correlation detection that continuously compares the measured zone loop current against the known random voltage pattern. The system uses the relationship between the transmitted voltage signal and the received current signal to detect zone status, providing feedback-based verification that distinguishes genuine zone changes from electromagnetic noise interference
Solution Approach 2:
The patent substitutes direct voltage measurement with current measurement combined with correlation analysis. Instead of measuring voltage levels directly (which are susceptible to electromagnetic interference), the system measures current flow through the zone loop and correlates it with the known random voltage pattern, replacing a vulnerable measurement mechanism with a more robust one
3Reliability
If correlation and autocorrelation calculations are performed to detect compromise, then the system can detect sophisticated compromise methods, but the processing complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-generating and storing the random voltage pattern in the control unit before it is applied to the zone loop. This pre-computed reference pattern is then used in the correlation calculation, eliminating the need for real-time generation and simplifying the processing requirements during the detection phase
Solution Approach 2:
The patent implements copying by creating a digital copy of the random voltage pattern that is stored in the control unit's memory. This copied reference signal is then used for correlation analysis against the actual zone loop current measurements, allowing the system to perform complex detection without requiring complex real-time signal generation hardware
Data Source
AI summary
A burglar alarm system with an input zone enhancer using a power source with random variable timing or voltage to supply the zone loop. The input zone enhancer measures the current flowing through a zone loop of a burglar control unit. A method includes providing random variable timing and a voltage to supply the zone loop. A method includes directly measuring the current flowing through a hard wired zone loop of a burglary control unit in order to overcome sensitivities associated with electromagnetic noise. A method includes detecting compromise attempts by calculating a correlation of two signals, the zone loop current and the reference current, and by calculating the autocorrelation of the zone loop current with itself at different points in time.