https://youtu.be/jKnUWHRe00w

Alerts employees when visitor enters or exits. Ding-dong tone with high-low-off adjustable volume control. Light-reactive sensor has sensing distance of up to 15 feet. May be used with door open or closed. Mounts easily on wall or door frame. Operates with 4 AA batteries or Tatco 16300 Adaptor (sold separately). Gray.

Size: 4 1/4"H x 2 3/4"W x 2"D.