MUL T LOCK GotU Digital Door Viewer with Bell Keys •Recessed curvature provides virtually airtight Rosette Style:Regular •Recessed curvature provides virtually airtight construction preventing smoke damage •Anchor Bolt for bolting safes to the floor on all models except HS 1750E The HS 750E recessed curvature provides virtually air tight construction preventing smoke damage during a fire as well At the same time Also as the door bell is pressed the camera will automatically take a photo of the visitors and the photo will be stored in the TF card in case the host is out so as to check the visitor's identity or to use the information for security purposes