The Avaya Definity TN777B Network Controller (TN777B) is   R6 and earlier Communicates control channel messages between the processor circuit pack and the distributed network of port circuit packs on the TDM bus Controls 4 data channels that process and route information directly from the processor circuit pack to customer connected equipment Has time of day clock with battery back-up for power failure or low voltage conditions Monitors the status of the system clocks and alerts the processor circuit pack in the event of a failure of any clock Supports ISDN Replaced by TN794 Network Control/Packet interface for R7 and R8 Replaced by TN2401 Network Control/Packet interface for R9 and R10 Fully refurbished