7960 -> CUCM 8.6 -> MGCP controlled FXO port on 2811 router -> PSTN emulator (another 2811) -> E1 trunk -> Public Router (CME) -. 7960
FXO port is set up to PLAR to the 4 digit extension on the CUCM hosted 7960.
Calls from the 7960 on the CUCM ring to the "Public" 7960 and will continue to ring until answered. As soon as the call is answered, the call drops on the CUCM 7960.
Calls in the other direction, from the Public 7960 to the CUCM 7960 proceeds to teh FXO port, the FXO port answers and PLARs the call to the 7960 on the CUCM. The CUCM 7960 rings once, and then drops the call.
Running a debug voice ccapi inout on the MGCP gateway indicates a disconnect cause code of 16 (which indicates normal call clearing)
It acts like its a codec mismatch.....
Its a lab so I can run debugs or provide configs if desired.
After a wee bit more digging - the fxs port on the PSTN box has battery-reversal by default.
My thought is when the fxo set to connected after the ringing stage the fxs in the PSTN box is
signalling a battery reversal which the fxo is seeing as a clear down.
Can you try turning this off on the PSTN router.
Hopefully this will resolve the issue and you can get your calls in both directions
Please rate useful posts.