NEC Univerge sv8500 Manual page 1317

[3] Loop-Back Test
Execute the loop-back test on the maintenance console.
(a) Line Loop-Back
All the channels (23ch) are looped back to ISDN on the ISDN line interface of MG(PRI).
(b) Payload Loop-Back
All the channels (23ch) are looped back to ISDN on the speech path control part of MG(PRI).
The difference between Line Loop-Back and Payload Loop-Back is;
Note:
All the processes in Line Loop-Back follow the timing of ISDN side. There are some processes following
the timing of system side in Payload Loop-Back. In other words, bit error may occur when the system does
not synchronize with ISDN in Payload Loop-Back. Bit error is not considered in Line Loop-Back.
(b) Payload loop-back
T
IP network
R
VOL.2-1064
MG(PRI) (1.5M) [SCA-24PRIA/MG-24PRIA]
(a) Line loop-back
R
ISDN
network
T
MG (PRI)