The power supply unit PS00D04KNX provides the system power necessary for the KNX/EIB bus. The connection to the bus line is via the bus connection block located on the front side. The integrated choke prevents the data telegrams from shortcircuiting on the bus line. When the built-in reset button is operated (press the RESET button for at least 20 seconds to reset the KNX Bus), the bus devices are returned to their initial state. For each bus line, at least one power supply unit PS00D04KNX is needed. Up to two power supply units may be attached to a single bus line. The distance between power supply unit PS00D04KNX and any of its bus devices must not exceed 350 m. The power supply unit PS00D04KNX has a voltage and current regulation and is therefore short-circuit proof. Short power failures can be bridged with a backup interval of approximately 200 ms. The power supply unit PS00D04KNX can supply DC 30 V power from an additional pair of terminals.