AT&T MERLIN LEGEND Communications System PBX System Planning Manual page 86

Trunks
An important part of the NTM review is to ensure that the synchronization
integrity of the network-both this communications system and its far-end
connections—is protected. To facilitate their evaluation, prepare the "Network
Planning Map" on page 7 of Form 3c. Describe the entire network of DS1
facilities by summarizing the following for each 100D module:
CSU used
distance between the control unit and CSU or far-end connection
types of facilities or services connected to each 100D module
clock synchronization source
As an example, the system described in Figure
module system with two 100D modules.
The communications system in Figure 3-2 is configured as follows:
Module 1 in slot 04 is connected to a model ESF-T1 CSU that is
approximately 100 cable feet from the control unit. (The DS1 facility is
connected to the ISDN-PRI network.)
Module 2 in slot 05 is connected to a 551-T1 L1 CSU that is approximately
160 cable feet from the control unit. (The far end is another communications
system.)
The primary clock synchronization source is the ISDN-PRI network
connected to Module 1. Its path is shown by a line and the letter P.
Note: The dotted line between the control unit and the PBX in Connection 2
indicates that the PBX derives its timing signal from your system.
The secondary clock synchronization path, shown by a line and the letter S,
is the system internal clock.
shows a large processor
3-2
Trunk Options 3-31