I have one remote site out of 25 that has an intermittent problem with calls coming into a 2821 router (h323) FXO ports and ringing to shared extensions on 7941/61 phones. Many times, the phones with the shared extension will ring twice, then the ringing stops on the phones. But the external caller is still connected to the call, and hears ringing. The call can not be picked on the phones with the shared extension, but if the employees wait a few more seconds, the ip phones will start ringing again, provided the external caller is patient enough to stay on a call that has not been answered.
These shared extensions do not forward no answer. And most of the time ring properly. This has happened before, and I was able to get it to stop by changing the voice-port impedance from the default 600r to complex1. This worked for a few months, and now the problem has returned.
Anyone have any thoughts?