FXO / FXS modules pinout

There are PCI boards with FXO and FXS modules available in the market.
My plan is to use this small FXO / FXS modules in a raspberry pi , but I need to know the FXO / FXS modules pinout (preferable the datasheet).
Anyone have it from any company?



As I understand it, the difference between the two ends of an analog phone connection has nothing to with pinout, since there are only two wires anyway. The difference is that the FXO (exchange) end supplies power, while the FXS (handset) end expects to receive it.

I believe they are referring to the P1 (3 pin) and p2 (20 pin) connectors on modules like the one in Digium X100M FXO Module and Digium S110M FXS Module

I suspect that this information is not in the public domain,

Incidentally, it looks like the FXS module uses a lot more pins than the FXO one, and does a lot more.

Correct… Many years ago I got a Zycoo Chinese ippbx with 4 modules inside, three FXS and one FXO. The module looks like other modules used in PCI boards for PC… And also these two modules you have commented here. I believe the pinnout of these modules are similares, so my idea is to understand how to use these modules and set a raspberry in order to use it…
The objective is to develop a very simple raspberry pbx with FXS and FXO ports.

I would think the simplest solution would be to use something like


I would think that the A/D and D/A are on the main board, and some of the hybrid may be. There may also be voltage conversion on the main board, although the number of passive components on the FXO module could suggest that some of the hybrid is in the modules.

I wonder why you need so many electronic components to implement a signalling protocol that dates from the 19th century, before they even had the concepts of “electronics” or “signal amplification” …

The FXO module may still be doing caller ID signalling detection, which is late 20th century. It is also probably providing the hybrid function, which, I believe, was done with transformers, in the 19th century.

Ring detection would also have been just connecting a bell coil across the wire and, basically relying on a human to do the the detection.

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