Internally the unit features 4 switches, which can be used to simulate a fire or fault on each of the zones. There are two pushbuttons, one for each zone, which simulate a fire by connecting the two cable cores when the button is pressed. Similarly there are two switches, which under normal conditions connect the end-of-line resistor across the cable, for each zone. However when the switch is changed, this create an open circuit which in turn raises a fault on the controller. Via these switches it is easy to functionally test the system.
