Integrated Services Digital Network private branch exchange with auto-synchronization clock selection has priority selection stages in priority chain configuration

摘要

The Integrated Services Digital Network or ISDN private branch exchange or PBX has a number of priority selection stages coupled in a priority chain configuration for emitting a frame synchronization output signal and a data clock output signal and a number of remote network chips connected to a network termination unit via a remote network interface. Independent claims are also included for the following: a method of automatic synchronization clock generator selection and a control method for digital phase-locked loops.