I have a PSTN line terminating on a FXO port on a router. This PSTN line is opx plar'd to an IP phone (so the IP phone is tied to the PSTN extension). The voice-port appears to require "supervisory disconnect anytone" to allow the IP phone to realise that a PSTN user has ended the call, and this works. However, sometimes the call is disconnected mid-call, and I can't see anything obvious.
