Thanks, guys, thats very useful info!
I am surprised the wifi not working as well as cellular.
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As far as the main topic is concerned we're looking at the QSC MP-M40.
It actually has a USB mp3 player that can host the pre-recorded files and a "panic button" file.
As well as recording on the app and then sending/uploading to the core a message, it's not live, but it is almost live which works well.
Embedded solution is a big pro.
User profiles with restrictions so we can have admin, security, user, front desk, etc... with different user privileges.
Future wall controllers are nice too.
Thanks!
I too am surprised the 4G radio works better. I am thinking some sort of stateful issue with NAT was causing issues. If the Unity server and the phones are in the same network, AP's with QoS are used (use the same precedence value as VoIP) you should be good to go.
I am going to setup my own Unity server for testing, I like the solution, but for this application it seems like way overkill.
I would run Asterisk or another SIP server on a Raspberry Pi and use a SIP to E&M gateway to get the audio to a balanced output. You could use any SIP Softphone client on your phone and dial an access code for live paging (could even setup zones). You could also record your announcements and trigger them from a web page hosted on the Pi or by dialing a code on the softphone.
If you have a BSS London it has a SIP client so you would not even need the gateway.