Arrangement for deriving a local clock in a packet cable telephony modem

摘要

A broadband terminal interface unit for use in an HFC communication network includes a phase-locked loop for providing a smooth transition between a CMTS-provided "national" clock and a local clock when the CMTS clock is lost (or before it is required). By controlling the tracking range of the PLL, the sensitivity of the circuit is controlled so that some drift in the national clock can be accommodated without unnecessarily reducing the performance of the components within the broadband terminal interface unit.