... Features: 1) True effective measure: voltage, current, active power, reactive power, power factor, frequency, Kwh, etc. Total 28 electrical parameters ... active power, reactive power, frequency power factor etc., set freely.6) RS232 or RS485 communication, Modbus RTU protocol.7) With power down ... memory function for KWH / KvarH.8) Power supply: 18--30V AC/DC ...