1, 2, 4, 8, 16 pdh fiber optical multiplexer Provides 4e1/8e1/16e1 the g.703 connection Realizes long-distance monitoring of this end equipment to the far-end equipment Provides function of ordering 4e1/8e1/16e1 to loop return from the remote end, fiber self-loop at local end; and provides a group service telephone interface (to select) Three power supplies: dc-48v, dc+24v or ac220v Transmitting range: 2-120km The double filament bidirectional and the single filament bidirectional type may select Conforms to the telecommunication level operation Requirement, and does not have the fault time equally (mtbf) above 100, 000 hours