Abstract: A building block having side walls and a front face perpendicular to these is provided with two rows of coupling pins on one side of the front face and counter-coupling tubes on the other side for mechanically coupling two building blocks by means of a clamping action. In each row, each second coupling pin has an electrically conducting surface, while the coupling pins lying between these are electrically insulating. One row of conducting pins is displaced in the direction of the rows by one coupling pin from the adjacent row. On the other side of the front wall a contact bar is arranged which is connected electrically with the conducting coupling pins of an associated row. The bar has a contact area for producing electrical contact with a row of conducting coupling pins of an adjacent, coupled building block.