Your answer is interesting. I posed a question about this some time ago and never received a response. I am not looking for an automatic fail over to the PSTN as I do not want long distance calls going out on the PSTN unless I specifically direct it, but it doesn't seem to me that some sort of notification that the network is down would be an unreasonable request. I have tried pointing my Outbound call route both directly to sp1 and using a trunk group but either way it takes about 45 seconds before I get the message "...has not received a response from the service provider". I waited more than 60 seconds before dialing to be sure the registration should have failed, and I also dialed more than once to see if it would work on the second try. I seems to me the Obi should give fast busy once it has determined that I have dialed a valid number and the service provider is known to be down.