... freely.6) RS232 or RS485 communication, Modbus RTU protocol.7) With power down memory function for KWH / KvarH.8) Power supply: 18 ... , Voltage Meter, Ampere Meter, Counter, Tacho Meter, Frequency Meter, flowmeter,Timer,Timer Relay, Solid State Relay, Proximity Sensor, ,Pressure sensor ,load cell ...