Fig 68
Two-stage Flow Diagram
Two-stage mode dial twice: User of IP side dials FXO number first ( Figure 63), then
FXO port off hook, user of IP side will hear the dial tone, then dials for the second time,
reaches callee through PSTN Switch.
Under Two-stage mode, billing of IP-FXO phase is always earlier than of FXO-PSTN phase,
and sometimes this situation may happen: billing of IP side has started already but PSTN
side is still not get through.
6
6
.
.
3
3
.
.
2
2
P
P
S
S
T
T
N
N
-
-
T
T
o
o
-
-
I
I
P
P
PSTN-To-IP can be divided into PSTN-FXO, FXO-IP, and has 3 modes: normal mode,
Auto mode, and dual mode.
6
6
.
.
3
3
.
.
2
2
.
.
1
1
N
N
o
o
r
r
m
m
a
a
l
l
M
M
o
o
d
d
e
e
