I have one main site with CM 4.1 and unity. I have a remote site that?s is connected of a WAN. The Main number for the remote site comes in across the E1 circuit at the main site then goes across the WAN link. How can I ensure the remote site can still receive calls on their main number if the WAN link goes down? Is there a way I can monitor the WAN link and if it goes down route the main number back out the PSTN to a single POTS line at the remote site?