The Signamax 065-79LX4WDMx1550 series models are Small Form-factor Pluggable (SFP) multimode fiber modules that support Gigabit Ethernet or SONET OC-12 over a single strand of singlemode fiber cable at distances up to 10 kilometers. There are two types of models in this series: one transmits at 1310 nm and receives at 1550 nm (model 065-79LXnWDMA1550), and the other transmits at 1550 nm and receives at 1310 nm (model 065-79LXnWDMB1550). These modules are designed to be used in pairs facing each other across a single stand of singlemode fiber. The “n” in the part number refers to the first digit of the typical distance spanned in kilometers (4 = 40 km). They are a cost-effective method of providing changeable Gigabit Ethernet or SONET OC-12 single-fiber singlemode interfaces to switches and media converters equipped with a standard SFP slot.