The difference configuration of digital and ip-based systems are the connection between controller to the next controller and connection from controller to the videophone unit.
Digital system uses a master unit which can serve up to 4 line buses (loops) where each loop can hold up to 8 sub controller units, so the system able to connect maximum 32 sub controller units.
Every controller where is placed at each storey can be connected until 16 videophone units or 32 audiophone units. So the master can serve up to 512 videophone units or 1024 audiophone units.
Digital System can be devided into several categories such as : Small, Medium, Large and PBX System
Regarding ip-base, the system can cover unlimited ip-videophone house unit (9999 units) . There is no need master and sub controller, except 1 unit ip-Guardphone and 1 unit ip-lobbyphone (expanded up max to 4 unit ip-lobbyphone). At each storey you have to provide POE gigabit switch to serve each ip-videophone house unit directly thru cat6 cable type.