NTD12 Dual-port DTI/PRI card description and installation Page 127 of 188
ISDN PRI Installation
Clocking
Clock operation
There are two types of clock operation - tracking mode and free-run mode.
Tracking mode
In tracking mode, the DDP loop supplies an external clock reference to a
clock controller. Two DDP loops can operate in tracking mode, with one
defined as the primary reference source for clock synchronization, the other
defined as the secondary reference source. The secondary reference acts as a
back-up to the primary reference.
, a Meridian 1 or Meridian SL-1 system with dual
CPUs may have two clock controllers (CC-0 and CC-1). One clock controller
acts as a back-up to the other. The clock controllers should be completely
locked to the reference clock.
