[Asterisk-Users] Busy and Unavailable

[Roger James]

If am trying to set up a virtual office using asterisk. I would like the voicemail to say Unavailable (or better ..not present) when a local extension phone is not registered and only say busy when the phone is actually busy. I am currently using SIP for my local extensions. However whenever a SIP phone is not registered asterisk reports the extension busy. Am I missing something here. I am not limited to SIP I could use any other channel for which there are windows clients available, however the IAX2 channel appears to behave the same.   I am sorry if this has been asked before but I could not find a way to search the mail archive. I suppose that is my second question J   Roger