SPECIFICATION:Used for AC three phase four wire active energy measuring. DIN rail installation type, ... standardAccording to IEC62053-21 standardFUNCTIONS:Total energy= positive active+negative activePhase failure indicate function for A/B/C phase voltage Display function ... A,Reference frequency:50Hz, 60HzStarting current: 0.004IbConnection type choice: three phase four wires, up in down out,L1,L1,L2,L2 ...