Instruction manual

FEATURES AND SERVICES
synchronized to the AT&T Reference Frequency, then it can be used as the synchronization
reference for the System 25.
DS1 Interface Circuit Pack
The TN767 circuit pack is the principal hardware element connecting System 25 to the T1
facility interface.
Two DS1 circuit packs may be mounted in the System 25 cabinet(s). Each
DS1 facility interface CP supports up to 24 trunks (23 if common channel signaling is used).
The TN767 CP emulates the TN747 CO trunk CP, the TN753 Direct Inward Dialing CP, the
TN760B Tie Trunk CP, and the TN742 Analog Line CP. This means the TN767 can be
administered to replace existing CPs that support automatic tie trunk, delay dial tie,
immediate dial tie, wink start tie, ground start central office trunk type, loop start central
office trunk type, direct inward dial trunk, and off-premises station line.
The trunk type can be selected on a port-by-port basis for each of the 24 ports of the TN767
CP.
The TN767 monitors the T1 facility for errors such as loss of signal, framing errors, and bit
errors.
DS1 Interface Network Synchronization Circuit Pack
To provide T1 facility interface in System 25, in addition to the TN767 CP, one other CP is
required. The ZTN131 CP synchronizes the System 25 to a master DS1 data stream,
monitoring the reference clock,
and maintaining a stratum 4 clock for synchronizing
transmission on all DS1 ports.
Wiring
The DS1 Interface uses shielded cable to connect the TN767 CP to the T1 facility or the CSU
if connecting to a public network.
Emergency Transfer
A T1 line cannot be switched over to an analog phone for emergency transfer. Therefore, the
System 25 should have at least one analog loop or ground-start line if emergency transfer is
needed.
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