Ideally what you would want to do is stick up an XML page on one of your call managers. Your IP phones (I know the 7940 and 7960’s are capable of this), then need to point to this XML. So if you goto config options on the phone. Select (3)for network config, and then select IDLE URL destination (35), you can add this to your phone. If you have many phones and TFTP server you can set this here.