The 3Com 3C10116C terminates a standard voice T1/PRI circuit into the SS3 NBX or NBX 100. Includes an 10 MB MDI uplink port for connecting to a LAN switch port to optimize network loading. (Not supported by the NBX 25 system). Blue colored faceplate version. Please let us know if you have any questions on the 3C10116C NBX T1 module.