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Joined: Thu Nov 24, 2022 10:51 am

Use Raspberry Pi / GPIO as FXS bridge between Fax machine / VoIP

Thu Nov 24, 2022 11:05 am


Bit of a strange one, for sure.

I used to work for a VoIP company and, whilst it's not essential - I have an AIO Printer / Scanner / Fax and would like to connect it to a phone line. Only, I don't have a phone line.

I know that there's probably a few FXS devices that I could purchase and connect to my network but I have a small collection of Pi 3's and a Pi 4 and would like to use one of these for a project.

Wondering if there's an existing solution out there, or something that I might be able to do to "simulate" a phone line socket using the GPIO pins of the Raspberry Pi? So, the fax machine can trigger an Off Hook, receive a simulated dial-tone from the Pi, then the Pi listen for DTMF tones, then trigger a SIP invite to VoIP provider?

Before anyone mentions pitfalls of dial-up data over VoIP, I'm well aware of the potential issues. However, I'll be using g711 so should be able to pull that side of it off. It's just an interesting idea for a small spare time project.

Posts: 5113
Joined: Tue Jul 02, 2019 2:28 pm

Re: Use Raspberry Pi / GPIO as FXS bridge between Fax machine / VoIP

Thu Nov 24, 2022 2:14 pm

You could but you'd be basically building your own FXS interface hardware which isn't trivial. ... xs-dongle/ is a made from scratch USB to FXS interface.

FreePBX for Pi and an off the shelf FXS interface would be the easiest option. "Easy" being a somewhat relative term when Asterisk is involved...

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