Connecting a paging system to a Communication Manager gateway as a station is significantly less complex than connecting it as a CO trunk. Compare this post to my immediately previous post about paging via trunks.
Most users understand that “to get an outside line”, they have to dial some number first – most commonly the digit 9, but sometimes other digits are used. When the user does that, they’re triggering Automatic Route Selection (ARS) functionality, which tells the phone system to automatically figure out how to route the digits that follow the access code.
With the appropriate equipment, Avaya Aura CM sites can “survive” an outage. An outage, in this context, means that the site lost IP (or TDM shudder) connectivity to both its primary controller and its enterprise survivable server (if there is one). The necessary equipment includes (generally) a media gateway with a local survivable processor, and some form of trunking (if you want calls to be able to leave the gateway).