is connected to directional coupler 21 which directs the signals to the second mobile station ms2 the apparatus illustrated in fig1 can therefore be used to test the effects of attenuation on signals between mobile stations and base stations by varying the attenuation in attenuators 24 and 25 since the environment is a closed environment signals will not be influenced by unwanted factors such as interference weather conditions etc and automatic repetitions of tests can be conducted on the cellular system fig2 a 2b illustrate an air interface with four mobile stations and three base stations in one embodiment of the present invention in this example each mobile station is connected to an individual directional coupler 50 each directional coupler 50 divides the radio path going to and from the mobile station into an up link path and a down link path referring now to the up link path the signal from the mobile station is attenuated in attenuator 60 and applied to a divider 70 the divider 70 splits the signal into four different paths for example the up link signal from mobile station ms1 is divided in divider 70 into four paths b0 b3 since there are only three base stations the path b0 is terminated the paths b1 b3 are then attenuated in variable attenuators 80 the three paths b1 b3 are then sent to different combiners 90 each of the four mobile stations has an up link path connected to each of the combiners 90 as a result each combiner 90 has.