Why combining two unreliable sensors makes one reliable one — and why that's a false-alarm fix, not a sensitivity upgrade.
A passive infrared (PIR) motion sensor is genuinely easy to fool. So is a microwave motion sensor, on its own. Put both in the same housing and wire them so that bothhave to agree before the alarm fires, and the combined sensor becomes far harder to fool than either one alone — not because two sensors are simply "better than one," but because of a specific, deliberate logic decision that trades a small amount of sensitivity for a large reduction in false alarms.