This hub is the heart of the Channel Vision Cat5 Intercom System. When you begin to build your room-to-room system, start with the Channel Vision Cat5 Intercom System Hub and add on. By connecting door stations (sold separately), you can call a specific room just by picking up a remote control. You can also press "page" to call everyone in the house. Convenient communication for your home starts here. Up to four Intercom System Hubs can be linked together to create a 24-room intercom system. The dip switches located near the Link In connector allow each hub to be identified by a letter, such as A, B, C or D.