The audio signal is processed by analogue to digital conversion, windowing, i.e. sampling of 20 ms blocks, pre-processing fast Fourrier transform analysis of frequency spectrum, and encoding according to psycho-acoustic aspects, i.e. irrelevant frequency components are weighted accordingly or discarded by means of a computer. The signal then passes via the transmitter and a communication channel which can now be of a narrower band-width, to the receiver. It is then decoded and the time domain signal is restored from the frequency domain digital signal. The uniform, continuous digital signal is then restored and, finally, passes through a d-a converter. 
VERFAHREN ZUR UEBERTRAGUNG EINES AUDIOSIGNALS.