Now when the building comes in, there is a display screen next to it. What's that for?

This is an access control system, which is installed at the door of the unit and is available in every household. The doors of the unit are generally equipped with security doors, so you can't enter the unit without a key. When there are visitors, press the visiting room number (usually room number) outside the security door downstairs, and then connect with the indoor access control system to make a visual call. Indoor personnel can open the downstairs security door by operating the indoor access control system to let visitors in.