Technical information

Troubleshooting and Repair
83
T1 Trunk (D4 DS-1)
A T1 Trunk is a digital trunking standard that supports multiple users.
Unlike analog trunks, the T-1 hardware signaling layer is independent
of trunk usage; synchronization & signaling are dealt with separately.
Synchronization
The T1 trunk establishes and maintains a connection between the
two systems. Sampling clocks of each partner must be
synchronized.
 The Master-Slave arrangement defines the leader and follower;
if connecting to a Public Network T1, the PBX will always be a
slave.
 The stratum clock levels define the accuracy of the clock and the
ability to match with the incoming master clock signal.The higher
stratum number synchronizes to the same or lower stratum
number. For example, a Stratum 4 (PBX) clock synchronizes to
a Stratum 3 (CO/PBX/Channel Service Unit) clock.
 When the PBX is connecting to more than one T-1 signal,
choose the order of preference of clocking sources in CDE Form
44, T1 Network Sync (always choose a connection as close as
possible to the defined master source clock).
Figure 18: T1 Trunk Synchronization