Brinno MAS100 Wireless Motion Sensor for PHV1330 Hidden Front Door Camera For use with the Brinno PHV133012 Digital PeepHole Viewer Mounts outside your door and triggers the Digital PeepHole Viewer to take pictures of anyone at your door Provides added security by allowing the Digital PeepHole Viewer to record photos of who's at your door even when you're not home Wireless operation; no wiring required Operates on 2 AA batteries (included)