Verilink Access Manager 2000 (896-502037-001) Product Manual - Manual (Page 310)

Monitoring and Troubleshooting Access Manager
8-40 Access Manager 2000 User Manual
To help you quickly isolate problems within the transmission path, most
of the Verilink CSUs (including NCC, CCC, or TAC) provide the
following four basic loopbacks shown in the following diagram.
These include the following loopbacks.
■
LLB , or Line Loopback
■
PLB , or Payload Loopback
■
RLB , or Repeater Loopback
■
ELB , or Equipment Loopback
All loopbacks can be activated and deactivated via the data port, the
diagnostic interface port, or an ESF 4 kbps message received from the far-
end CSU or an intra-network device, except as described in the previous
section.
CSU loopback
descriptions
NETWORK
INTERFACE
CSU
DTE
SIG
PROC
CRIT
PROC
Repeater
LLB RLB ELB PLB
LBO
EQ
OUT
SM
IN
EQ
MON
SM
OUT
EQ
IN
SM
MON
NETW
ORK