The power supply unit provides the system power necessary for the bus system. The integrated choke prevents the data telegrams from short-circuiting on the bus line. The connection to the bus line is established by clicking the device onto the DIN-rail (installed data-rail) or by using the bus connection terminal (red-black) on the front side. The power
supply unit NT640-4 can supply DC24V power from an additional pair of terminals (yellow-white). This DC24V output voltage is only allowed to power an additional line via a seperate choke.