I am wondering if you can interface a standard, RJ11 telephone through GPIO, and input an output through the phone, even using asterisk to connect to voip. The phone I have is a GE model number 29255ge2 which I believe was made around the late 1990s and early 2000s. I am wondering if you can remove the RJ connector from one end, somehow connect the red and green wire to gpio. One concern I have is that 5 volts will be enough to power the phone, and also making it ring, I know normal ringing voltage is 60v AC I believe.

BTW I am not connecting this to the phone line, also basically if you are misunderstanding this I am basically trying to use the pi as cheapo Analog Telephone Adapter.

  • 1
    The Pi's GPIO are 3V3 and can drive perhaps 20 mA. What signals do you plan to send down the phone line? Would connecting non-approved kit to the phone line be legal in your jurisdiction?
    – joan
    Oct 4, 2015 at 22:16
  • Not to mention what is on the other end some phone lines send a very high voltage for the ring - which would instantly fry your Pi. What is the actuial goal? beyond connecting a phone to the Pi. Oct 4, 2015 at 22:22
  • I am not connecting anything to the phone line, I am connecting a phone to the pi, and basically I want to be able to make calls from it, its kind of a "because I can" thing and I don't care abount incoming ring that much. In fact, one of the reasons is because I don't even have a landline.
    – user22660
    Oct 4, 2015 at 22:51

1 Answer 1


So from what I understand you're trying to make the RPi into an ATA device. Some combination of GPIO pins are wired into a phone cable that plugs into a analogue phone handset.

Could be possible in a run-around way, with a DAC/amp circuit in-between, you could use I2C for audio i/o see this question for more info.

A couple of other options might save some hair pulling:

  1. Get a USB to FXS device like this - the one I linked has Linux drivers, so some possibility of an easy-ish job, then combine with something like RasPBX running on the RPi.
  2. Ditch the idea of using the RPi and just buy a cheap or used Cisco ATA and plug that into your analogue phone handset.

Personally I'd go with the second option and save myself about 50 hours.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.