... put voltage range and near zero tolerance on frequency and voltage variance on the put-put the H series ... Frequency46~54Hz or 50Hz±0.2(line mode)50Hz±0.2Hz(battery mode)WaveformPure sine waveDistortion3%4%Overload capability108%~150 ... , utility power, inverter, bypass, overload, faultAudible alarmBypass, on battery mode, battery low, overload, faultAcoustic noiseAt 1 meter distance45 dB50 ...