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YisTech Wireless Motion Sensor Detect Alert, Home Security Driveway Alarm, Motion Detector Store Door Entry Chime Doorbell, Caregiver Pager for Elderly/Kids (1 Motion Sensor 2 Receiver) - Amazon.com
How do motion sensors work? Do they detect movement through walls and floors, or just those directly in front of them? - Quora
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Amazon.com: Y DIANS S Motion Sensor Alarm 120dB Horn Adjustable Volume Tones Waterproof LED Strobe Light Sirens Motion Detector Alarm System for Home Factories, Warehouses and Docks Security AC110-120 V SLA-01W :
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