Cisco NM-4B-S/T enterprise networking (router/Catalyst switch/UCS families) Router Line Card

The Cisco NM-4B-S/T is a 4-port ISDN Basic Rate Interface (BRI) network module with S/T interfaces, for Cisco’s modular access router platforms including the 2600 and 3600 series. Each BRI port provides two 64kbps B-channels plus a D-channel for signalling, giving up to eight simultaneous ISDN B-channel connections across the module’s four ports; the S/T interface expects an external NT1 (common in Europe, where the carrier network already provides U-interface-to-S/T termination). It suited branch routers needing dial backup, ISDN dial-on-demand WAN links, or aggregated remote-access dial-in over multiple BRI lines. It remains a routine spare for existing deployments still using ISDN BRI WAN or backup links. Confirm your target router platform, available network-module slot and interface type (S/T vs U) before ordering. This is a refurbished unit, shipped worldwide from Tech-Star’s UK stock.