7-inch wide Monitor: Main monitor lets you clearly identify visitors3 Monitors connectable: A maximum of three main monitor units can be connectedVideo Intercom Systems Picture Recording: Up to 50 images of visitors can be recordedElectric Lock Release Support (Door Opener): If optional monitors are connected to the system, you can use a monitor to call other monitorsIntercom Call: If optional monitors are connected to the system, you can use a monitor to call other monitorsHands-free Talking: When you receive a call from a door station,you can monitor the visitor on the monitor display and talk hands-freeNight Vision