About a week ago our BT8600 DECT phones stopped ringing on i/c calls although an old POTS phone that shares the phone socket with a Y adapter does ring. Various tests were done by removing the Y adapter and Extension sockets from play that suggested the DECT Base Station may be the cause. A new BT DECT 4600 system was purchased overnight and installed but this new system exhibits the same symptoms of not ringing on i/c calls. You can see the i/c call active on the DECT handset display and the call can be successfully answered on the DECT handset despite no ringing to alert you to the call. Outgoing calls are fine. I believe that it is highly unlikely that 2 separate DECT systems would exhibit the same symptoms on a service that has previously worked ok. The fact that this problem started within the last week, when the weather changed for the wetter, suggests an issue with the strength of the exchange generated ringing current or the master socket ringing current capacitor / filter, or other changes at the exchange end.. Any ideas other than an engineer visit which I have scheduled for this weekend?