Filter
Top Products
1-14 About the Vanguard 6435/6455
PRI Supplementary Service
Figure 1-10. D-Channel Only Messages
Frame Relay
QSIG
QSIG
PBX
PBX
QSIG
101
201
401
PBX
1
)
A
c
t
i
v
e
C
a
l
l
b
e
t
w
e
e
n
U
s
e
r
@
1
0
1
&
U
s
e
r
2
0
1
2) User @101 tries to make call to User @101
3) PB @101 sends back busy indication
4) PBX @410 "camps on" User @101 using
"D" Channel Only Messages
5) PBX @401 places call when User @101 is free