DUET combines innovative microwave technology with advanced PIR detection. The creep zone directly under DUET provides anti-sabotage protection. DUET employs signal processing technology using digital algorithms to differentiate real-motion signals from noise signals. A digital multiple-notch filtering technique eliminates these interferences. DUET memorizes and stores the tripping order of alarm occurrences for up to 14 arm/disarm periods. This provides vital information. If either technology is blocked, masked or malfunctioning, the trouble output is activated.