In a method and system for determining the composition of a subscriber loop, the method consists of analyzing the echo responses generated by the transmittal of pulses onto the subscriber loop. Shaft ends are fastened against rotation in the joint, the ends being held in a housing joint adjoining the two joints with interposition of a ball joint so that the ball of the ball joint is mounted for rotation about its center point in a socket of one shaft end and is slidingly movable in a direction of the shaft axis of the other shaft end. If the user moves his or her eyes or hands, the location of the 3D object may change accordingly.