Avaya S8700 Maintenance Manual page 1309

DS1-BD (DS1 Interface Circuit Pack)
Combined with a TN767E circuit pack, Avaya's 120A1 Integrated CSU module
becomes an enhanced CSU. The 120A1 CSU, combined with new switch
software and the functionality provided by a TN767E's hardware and firmware,
provides functionality equivalent to an external stand-alone Avaya ESF T1 CSU.
The 120A1 CSU connects to the TN767E circuit pack on the I/O connector panel
behind the port carrier, and thus becomes an integrated part of the S8700
Multi-Connect system. Throughout this document, the term 120A1 means a
120A1 (or later-suffixed) CSU.
The 120A1 CSU is for use in the United States of America with 1.544-Mbps DS1
service. For more information about the 120A1 CSU module see DEFINITY
Communications System Generic 1, Generic 2, and Generic 3 V1 and V2 —
Integrated CSU Module Installation and Operation, 555-230-193.
A TN767E and a 120A1 integrated CSU support on-demand loop-back tests
assisting fault detection between the:
TN767E circuit pack and the integrated CSU
Integrated CSU and an optional customer-premises loop-back jack
Integrated CSU and a remote CSU.
These loop-back tests are explained in detail later in this DS1-BD section, but
Figure 8-23 on page 8-588
The following list of acronym definitions are for
PLB = Payload Loopback
BLB = Board Loopback
ELB = Equipment Loopback
LLB = Line Loopback
RLB = Repeater Loopback
CLJ = Loop-Back Jack Loopback
R-LLB = Remote Line Loopback
SMRT = Smart Jack
LPBK = Loopback
For more information about DS1 interfaces, refer to the DEFINITY
Communications System DS1/CEPT1/ISDN-PRI Reference, 555-025-107.
555-233-143
gives a high-level overview of the loop-back points.
Figure 8-23 on page 8-588:
Issue 1 May 2002 8-587