Enterphone (intercom) systems can be installed on a building to let you know who is at the door or gate before they enter the property. Video cameras can be integrated into the intercom system for added security and identification. 

Enterphone systems are common in apartment building complexes, businesses, schools and hospitals but have applications in residential settings too. 

More sophisticated enterphone systems can have a digital directory on the main screen making it easy for users to find the person they are trying to reach.