NEC Univerge sv8500 Manual page 1200

Connection between STN A and STN B cannot be guaranteed.
ISDN
STN A
For a tandem connection involving Central Office Trunk (COT) and Loop Dialing Trunk (LDT), input level
Note 2:
can be lower than minimum DTMF detection level (-27.0 dBm) at MG-PRI/PRA because of Line Loss be-
tween two switches.
If input level at MG-PRI/PRA is lower than minimum DTMF detection level,
DTMF relay cannot be guaranteed.
MG-PRI/PRA
STN A
Tandem Connection Involving Media Converter (MC)
MG-PRI/PRA
Tandem Connection Involving COT or LDT
ISDN
DTMF
relay
Input
IP Network
2-wire
Line Loss
The signal can be attenuated here.
If input level is smaller than -27 dBm,
DTMF relay cannot be guaranteed.
VOL.2-947
MG-PRI/PRA
MC STN B
COT/LDT
LC/LDT
LC
STN B