How do I connect an Arduino to a landline telephone wall outlet?

I'm thinking of home automation, something like:

  • I call my house, and after a few rings the Arduino picks up the phone
  • The Arduino somehow (modem? synthetic voice?) tells me the house temperature and whether I've left my garage door up and all the lights turned on.
  • I somehow (modem? whistling Morse code?) tell the Arduino to lower the garage door, turn off all the lights, and adjust the temperature setpoint down a few degrees.

Is it true that connecting stuff to a landline (i.e., technology developed in the 1870s) is less complicated than connecting stuff to some sort of cell-phone network or cable TV Internet access?

(This is a different question than " I'm looking for a low-parts-count Arduino <-> phone & POTS line interface " , right?)


1 Answer 1


Here is a project that someone did a while ago that seems similar:


He details the DTMF chips he used and gives a sample sketch and schematic. But he also brings up some potential legal issues.

I think given the legal issues and the interface issues (synthetic voice, Morse code, etc.) I would go with a cellular interface and use text messaging to talk to the system. In which case Sparkfun has a bunch of stuff to do just that including an Arduino shield that accepts a SIM card.


I'm in the planning stages for a cellular project and this shield seems like a really nice solution for prototyping. And they offer the standalone module as well.

  • \$\begingroup\$ I wouldn't recommend cellular, even if you're scared of Part 68; VoIP would be a better solution in that case. \$\endgroup\$ Commented Dec 2, 2020 at 18:49

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