Each TCC+ card contains two RJ-45 connectors labeled Primary and Secondary, on the front panel. These connectors are for a primary and secondary (redundant) Stratum 3 external clock reference source that is traceable to a Stratum 1 clock source. The external reference source allows the Cisco uBR10000 series reference clock to be synchronized to the Stratum 1 clock source, providing a free-running DOCSIS-quality clock reference and timestamp to the cable interface line cards. The TCC+ cards monitor each other's priority information, so that if the active card fails, the active card role is transferred to the redundant backup card without loss of data.