The OM8000 series PDH Multiplexer is a kind of highly effective fiber-optic communication device which can use fiber optic to transport several E1 signals in the meantime and can test the used E1 automatically, the flexible circuit test and the indication function has a simple single panel form, which provides a 10/100M linearity Ethernet port (can choose), the official telephone function (can choose) to raise the flexibility of application as well as enlarge the utilization of the fiber optic.