When I am on a call on my cellphone (Android with Tmobile), and the other caller puts me on hold, a message appears on my phone’s screen that the call has been put on hold. I assumed this was a feature that is exclusive to either cellphone calls or to Tmobile.
However today I was on call on my cellphone with someone on a landline via a PBX. When they put me on hold, I got the same message that the call has been put on hold.
My question is, does anyone know what this is and whether FreePBX/Asterisk supports sending these messages/signals?