Abstract: A Signal Activated Door Hinge is typically a three-hinge door's central hinge. The lower part of the hinge plates attaches to an upper sprocket pinned to a lower sprocket which supports a central drop shaft extending to the bottom of the cover tube. An annular drop weight slides on the drop shaft, latching to a pivoted release lever near the drop shaft top. A bi-metallic muscle wire controls the pivoted release lever. As electric signal reaches the muscle wire, the release lever rotates away from the drop weight which unlatches and slides down the drop shaft under gravity, impacting the bottom of the drop shaft and pulling it down to open the sprocket connections. A coiled spiral activation spring inside the upper sprocket unwinds, rotating a hinge plate. To reset, the signal is canceled and the drop weight raised to the latched position in the release lever.