When visitors press the doorbell button on the door viewer camera the doorbell will ring inside of the room. At the same time, the screen inside the door will turn on automatically to show the outside images and will last for 20 seconds before turning itself off. 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.