DDSY39 (LED) single-phase prepayment static energy meter is which adopts based on special large-scale integrated circuit and SMT technology, adopting industrial elements and components with long lifetime introduced form abroad. It preserves data under power-off situation. This product conforms to IEC62055-21-2005 & GB/T18460: Electricity metering, prepayment systems. and IEC62053 & GB/T18460.3- 2001: class 1 and class 2 static AC active watt-hour meter.