1.Automatic charging in UPS off mode 2.Zero transfer time 3.Smart RS-232 communication port 4.Optional ... Panel indication LCDInput,oupt,battery voltage,frequency,load rate,UPS state, temperature LEDMain input , bypass,Inverter,Battery ... unit85% Communication1.Power status 2.UPS shutdown 3.monitor UPS status 4.UPS self test 5.auto-save files ... --40 °C Humidity0%-95% Low Frequency Online UPS TA2K-20K