NTI Audio ML1 Minilyzer, Analogue Audio Analyzer, For sound level (RMS, relative, peak), THD+N, VU & PPM, frequency, signal balance, polarity via built-in microphone, Time and frequency sweep, 1/3 Octave spectrum and envelopes, Acoust. SPL and Leq measurement only available with Mini SPL (available on option #154763#), Input: XLR and RCA, Power supply via 3x 1.5 V AA battery (not included), Case on option #154773#