An apparatus and method for controlling the transmission power of a DSCH in a mobile communication system is disclosed. One method includes specifying at least one codemark that is intrinsic to a computing system. The feed-trough includes two spring contacts which are configured to be spring compression push-fit in grooves in edges of the discharge-electrodes. The calibration device is adapted to receive the probe and has an optical filter for transmitting the measurement light signals but not the calibration light signal.