DDSY39 (LCD) adopts LSI &SMT industry element and long-duration element of international band. It meets the require ment of GB/T18460.3-2001:The third part of the IC prepayment sale system; prepayment meter. and GB/T17215-2002: Class1 and class2 static communication active meter. This product has functions of prepayment, load threshold control. They have the characteristics of small size, long-life high accuracy, good stability, low power consumption etc.