A200 Overhead Paging

Actually there are two types of analog paging adapters.

Type 1 - Provides battery towards PBX, this requires an FXO type interface on the PBX. In a type 1 connection the PBX comes "off hook" on the paging trunk and the paging adapter bridges the audio to the amplifier

Type 2 - Looks for battery from the PBX, this requires an FXS type interface on the PBX. In a type 2 connection the paging adapter comes "off hook" in response to ring voltage supplied by the PBX.

Variations include type 2 adapters that accept a DTMF digit for zone selection, overhead music inputs, integrated amplifiers etc.

Valcom and Bogen are very popular vendors in this space.

Valcom produces and IP SIP compliant analog paging adapter that supports 4 zones. They work great and list for under $1000.00

For a Type 2 system like Scott described above, another solutions is to split the wires: the two battery wires go to a proper power supply, and the two tip/ring wires can be connected to a standard audio wire coming out of a sound card (using a standard junction box).
Not sure if the trixbox appliance has a sound card in it, but if you can add one and keep the Sangoma card for better uses (or sell it) it's a cheaper setup and works just as well.

I've been finding this post in searches in both this web site and major search engines. So, I thought I'd update my success with similar equipment

I used a Sangoma A200 with both FXS and FXO module included, 2 ports each. Originally, this card only had an FXS module. These FXS ports did provide me a dial tone and an analog phone would ring. But, this setup did not work for my Valcom V-2003 4 zone paging system. After adding an FXO module, and after running "setup-sangoma", my Valcom did work properly.

The Valcom v-2003 is plugged into a wall electrical outlet. The switches are setup to Battery Feed off, and Loop start.

Once I connected the cable, the CLI in asterink announced it's connection. From there, I just created a Zap extension, the channel of the FXO port (1 in my case), and rang the paging system. I got a tone, pressed the needed number, and there I was, overhead paging.