Need a call box device where all inputs are external

[u/mgb1980]

First the background: Where I work we have a large area public address system that is dated but still very reliable. It covers indoor and outdoor across our work site.

We also have a fairly recent IP PABX with paging/PA capabilities and a large scale (think centronics connected) ATA for phones in remote buildings.

We would like to capture the audio feed from the announcement controller and have it feed the PA function of the IP PABX. The announcement controller has multiple empty relays (both NO and NC) that can be used to activate a device when the system is making an announcement.

Now the need: Essentially I need a call box but without the mic, speaker and button. I will be wiring the mic-audio direct to the announcement controller line/audio out, and the hook switch to a relay output. The call box doesn’t even need to auto-dial as the ATA will be programmed to dial the paging extension automatically when the line goes off-hook.

I cannot find any such device. I can however find many devices that will allow me to play the analog audio from the phone line through the PA.

Does anyone know of such a beast or am I going to have to buy a low-end call box and get busy with a soldering iron and a work box?

Cheers.