Noise-Tolerant Security Tag Using LF Interference Detection
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Solution Overview
Problem
Security systems using low-frequency (LF) technology in healthcare facilities are susceptible to interference from LF emissions from sources like PROX card systems and electronic devices, leading to incorrect locking/unlocking of doors and potential elopement or unauthorized access.
Innovation Solution
The security system includes a tag that detects LF noise and transmits an RF signal with the last received LF exciter ID, enabling the controller to send a lock command even in noisy environments, and analyzes noise characteristics to determine the source, allowing for appropriate locking or unlocking decisions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the security system uses LF technology for communication between controller and tag, then the system can operate with established low-frequency protocols, but the system becomes susceptible to interference from LF emissions from other devices
Solution Approach 1:
The patent detects LF noise from interfering devices and converts this harmful interference into a beneficial trigger mechanism. When LF noise is detected, the system interprets it as a signal to maintain locked doors, thereby transforming the harmful interference into a security enhancement that prevents unauthorized access during noisy conditions
Solution Approach 2:
The patent introduces RF communication as an intermediary layer between the LF exciter and the lock mechanism. The tag receives LF signals but communicates with the controller via RF signals, which are less susceptible to LF interference. This intermediary RF communication channel allows the system to maintain reliability while继续使用 LF technology for initial signal reception
2Reliability
If the system locks doors to prevent elopement, then security is improved, but authorized individuals experience delayed access
Solution Approach 1:
The patent implements dynamic door locking behavior that adapts to environmental conditions. Doors are locked under normal conditions to prevent elopement, but automatically unlocked when LF noise from authorized access devices is detected. This dynamic adjustment allows the system to maintain security while enabling timely access for authorized individuals
Solution Approach 2:
The patent employs feedback mechanisms where the system continuously monitors for LF noise patterns associated with authorized access attempts. When such patterns are detected, the system receives feedback that triggers door unlocking, creating a closed-loop control system that balances security with authorized access needs
3Loss of time
If the system unlocks doors quickly for authorized access, then access time is reduced, but security against unauthorized access may be compromised
Solution Approach 1:
The patent applies different quality thresholds for different access scenarios. The system requires detection of specific LF noise patterns with particular characteristics (frequency, duration, pattern) to trigger unlocking, rather than responding to any LF signal. This localized quality control ensures that only genuine authorized access attempts result in door unlocking
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution prevents unauthorized access and elopement by ensuring doors remain locked in noisy conditions and reduces waiting times for authorized individuals by enabling quicker unlocking when necessary.
Implementation Method 1
LF exciter 214 transmits, via antenna 216, a low frequency (e.g., 125 KHz) signal
Implementation Method 2
the tag's LF receiver 328 receives the LF signal transmitted by LF exciter 214
Implementation Method 3
RF transmitter 330 of tag 110 generates an RF signal that encodes the extracted LF exciter I.D. as well as the tag's 110 own I.D.
Implementation Method 4
RF receiver 218 decodes the received RF signal
Data Source
AI summary
A security system and method includes a tag that continues to function in the presence of LF noise by (i) detecting the LF noise, and (ii) generating an RF signal comprising information that causes a controller to issue a lock command.