The external unit must be Alba or Hero, with XE2922 installed in. Through Bluetooth technology, the mobile phone acts as a virtual external unit, so the smartphone replaces the door panel, so without touching it, the visitor will make the call to the internal unit, in fact he will select the chosen user from the keyboard that appears on his screen and will be connected to the push button panel without having had any contact. In short, another Farfisa app really in line with market demand, usable in a simple, fast and free way by anyone, always guaranteeing maximum security and safety