The Protech by Hirsch SDI-76‑A Indoor PIRAMID Sensor, a wide‑angle 75 ft × 75 ft dual‑technology intrusion detector engineered for professional indoor security applications. The SDI‑76‑A combines Stereo Doppler microwave and dual‑element passive infrared detection in an AND‑gated configuration, ensuring that both technologies must activate simultaneously before an alarm is generated—significantly reducing false alarms from environmental disturbances. Equipped with Lens A, the SDI‑76‑A delivers a broad 90‑degree coverage pattern ideal for open rooms, corridors, and large interior zones. The PIRAMID design incorporates balanced temperature compensation, enhancing motion detection reliability even as indoor temperatures rise above 85°F. This indoor model features rugged construction, walk‑test LEDs, digital range/sensitivity control, and compatibility with the optional FF‑3 fluorescent light filter, making it a dependable solution for commercial, industrial, and critical‑facility interiors.