An addressable node unit includes connections for at least two lines via which the node unit can be addressed. The connections are connected to a circuit which evaluates an addressing signal. The node unit includes at least one power source which is supplyable with power via at least one of the lines. A switch is provided in the path between the evaluating circuit and the corresponding line connection, the switch being opened after an addressing process so that the power supply of the evaluating circuit is ensured by the at least one power source after the addressing.