... tests each phase voltage value of two lines of power supply. When the voltage is lower 80% of rated voltage,it is ... (R), if each phase voltage of two lines of power supply is normal ,the controller will display NA,NB,NC,RA,RB ... at the same time. 5. Alarming function5.1 If one line of power supply is abnormal ,during the transfer period between the two circuit breakers, the ...