NEC SV8500, Manual

Page: 1317 / 3438

VOL.2-1064
MG(PRI) (1.5M) [SCA-24PRIA/MG-24PRIA]
[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).
Note:
The difference between Line Loop-Back and Payload Loop-Back is;
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.
LAN interface
speech path control part
ISDN line interface
IP network
ISDN
network
(a) Line loop-back
(b) Payload loop-back
T
T
R
R
MG (PRI)