... 40-70Hz)10) Fan speed varies according to load automatically11) Lightening and Surge protection 1050J12) Smart RS232 ... 1%(static load)Crest factor3:1Wave distortionLinear load <3%,Nonlinear load <5%Over load ability105%<load<125% for 1 mins ,125%<load<150% ... LED and LCD, clear & friendly display interfaceEfficiencyabove87%(full load)ProtectionOutput short circuit, Overload, Output low voltage, Battery ...