Abstract: A recorded voice test signal is transmitted from a transmitting end of a mobile communication system, and in a test unit at the receiving end a frame generator is synchronized with the received signal. Each frame of the signal is evaluated in computing circuits on the outputs of the frame generator, which calculate characteristic values of each frame which are then subtracted from calculated characteristic reference values of the frames stored in a memory. The differences between these characteristic values are fed to a neural network which classifies the quality of the difference signals as Good, Medium and Bad, and a defuzzyfication logic circuit further refines the quality classification output, whereby the transmission quality throughout the mobile communication system can be reprodicbly rated for a system quality rating.