Cisco Transport Shelf Controller for M2, M6 Chassis

The Cisco TNC, TNCE, TSC, and TSCE cards incorporate a highly stable Layer 3 internal timing reference to provide system timing based on input received from an external BITS source or from an incoming SONET or SDH optical signal. Synchronous status messaging helps the system select the best timing sources, and a holdover mode maintains timing accuracy when preprovisioned synchronization references are not available.