What is an Island in the Due Fili system?

It is an area of the system in which the devices (intercoms/video intercoms/plates) facilitate intercom communication; an example would be a front door unit (part no. 20577) linked with the Video door entry monitors in an apartment, where you want to allow local communication without interrupting any calls made from the Master plate (main outdoor station) to other apartments (islands). The island is electrically separated with a separator (part no. 692S) and a power supply (part no. 6922.1), forming a secondary branch which filters signals transiting along main backbone .