Avaya MCC1 Maintenance Procedures page 362

Additional maintenance procedures
DS1 CPE loopback jack (T1 only)
Figure 108: Network Interface at Extended Demarcation Point (Smart Jack inaccessible)
Figure notes
1 Span Section 1
2 Span Section 2
3 Span Section 3
4 120A2 (or later) Integrated
Channel Service Unit (ICSU)
5 RJ-48 to Network Interface (up
to 1000 Feet) (305 m)
362
6 Loopback Jack
7 "Dumb" Block (Extended Demarcation)
8 Network Interface Smart Jack
9 Interface Termination or Fiber MUX
10 Central Office
Maintenance Procedures
December 2003