Operation of the LOKAL Leakage Detection System by F.A.S.T is based on the technical principle of the frequency-dependent correlation coherence analysis. The pressurized medium inside the pipe generates a discharge-related noise at the leakage spot. This discharge noise propagates to both ends of the pipe section simultaneously and is acquired through sensitive pick-up units at accessible spots such as valves, hydrants, etc.. The amplified signal is then radio-transmitted to the coherence correlator and converted into cross power spectrumcompatible data by means of FFT algorithms. Further data processing provides coherence / correlation, which will be displayed on the LOKAL screen.