one or more of the number of noise generators 11 13 for providing a band limited noise signal rb for the hf signal hf for example the selection means 14 selects the first noise generator 11 so the band limited noise signal rb corresponds to the first masking signal m 1 see fig6 and 7 in accordance with which the first masking signal m 1 corresponds to the band limited noise signal rb with reference to fig7 the respective frequency band f 1 f 3 of the band limited noise signal rb is preferably set to at least a corresponding predetermined frequency band f 1 f 3 of a respective terrestrial base station signal b 1 b 3 of a base station the trigger means 15 can consequently be set up to carry out a plurality of functional tests in series with differently selected band limited noise signals rb in this instance the evaluation means 8 can be set up to provide a test result vector e as a function of the plurality of functional tests of the communication system carried out in series furthermore the error detection means 18 can be set up to detect an error f of one or more noise generators 11 13 and or an error f over the transmission path 2 as a function of the test result vector e provided before the functional tests are carried out in series.