Abstract: In a system for quality control evaluation of energized electrical power sources, a waveform analysis apparatus and method is employed permitting greatly increased capability for the detection, measurement and evaluation of the signal characteristics, especially the noise signal, of the tested units. A high-speed magnetic tape recorder stores the output signal of the unit under test. A high-speed AC-to-DC converter receives the output noise signal and inputs it to a fast-responding, track-and-hold peak detector. The peak level output signal of the peak detector may be displayed for any desired time interval and the peak detector reset resulting in discrete time interval printouts of peak noise output. Noise levels of interest may be rapidly located and a complete display of the power source output signals during that time interval of interest obtained from the magnetic tape recorder allowing detailed waveform analysis.