NARROW BAND AND SPREAD SPECTRUM SIGNAL Transmission OVER THE POWER Line IS USED TO FINDING THE LOCATION OF FAULT AND OTHER IMPEDANCE MISMATCHING ON POWER Line. IN THIS METHOD, SOME FORM OF WAVE IS TRANSMITTED ON POWER Line AND REFLECTED WAVES THAT ARE AS A RESULT OF IMPEDANCE MISMATCHING ARE RECEIVED. BY USING OF THE AMPLITUDE AND PHASE OF REFLECTED WAVES, DETERMINING THE LOCATION OF IMPEDANCE MODIFICATION WOULD BE POSSIBLE WITH A PROPER PRECISION.IN ORDER TO PREVENT THE ADVERSE IMPACTS OF TRANSMITTED SIGNALS ON THE POWER Line NETWORKS COMPONENT, SIGNALS HAVING LOW POWER SPECTRAL DENSITY ARE USED, WHICH A SPREAD SPECTRUM SIGNAL IS AS SO. AMONG SPREAD SPECTRUM TECHNIQUES, MAXIMAL LENGTH SPREAD SPECTRUM METHOD, IS MUCH MORE USEFUL BECAUSE OF THE EASE OF CODE GENERATION, WITH ARBITRARY LENGTH, HAVING LOW SIDE LOBE TO MAIN LOBE RATIO, HIGH RESISTANCE AGAINST INTERFERENCE AGAINST INTERFERENCE, JAMMING AND NON- STABILITY OF POWER LineS. AMONG NARROW BAND TECHNIQUES, MULTI PHASE MODULATIONS ARE THE BEST, BECAUSE OF LOW SIDE LOBE TO MAINE LOBE RATIO. FOR DETECTION OF LOW REFLECTION SIGNAL DUE TO IMPUDENCE MISMATCHING AND FOR SIDE LOBE REDUCTION WINDOWING TECHNIQUES IS USED. HAMMING AND HANNING WINDOWS HAVE FAIRLY PROPER PERFORMANCE AND IMPLEMENTATION OF THESE TECHNIQUES IS EASY. BUT DOLPH-CHEBYCHEV WINDOW HAS OPTIMUM PERFORMANCE FOR REDUCING THE SIDE LOBES.