A switch-extender is connected to a measurement system and to several DUTs. It splits a signal from the measurement system into several signals so that the several DUTs receive the same signal and can therefore be tested in parallel. The switch-extender further includes at least one amplifier and/or at least one attenuator for every output port so that every signal has the same signal level no matter what the individual attenuation factor of the signal connectors or of the internal printed circuit board is. Furthermore a method for calibrating the measurement system as well as for the switch-extender and the signal connectors describes how to obtain the needed calibration values both for the downlink path and for the uplink path without changing the signal connector.