One of my customers is moving soon and I’m probably going to suggest they use VoIP in their new offices. One of the features of their current analogue PBX that they use a lot is the connection to a public address (PA) system for paging people not at their phone.
Can Asterisk use say a standard sound card to connect to the PA?
yes. some paging system actually use an fxo or fxs port to connect to the pbx for paging you might want to check theirs. More info here
we had an existing analog PA, so we connected to that to one of our FXS ports on a secondary server, set up IAX trunking between servers, and now anyone can dial x9999 to get onto the overhead pager.
works great, and since it used existing equipment, it was basically free.
this may not be helpful to you, but at least you know it’s possible.