Interfacing with a Telephone line

Hi everyone,

I need to dial a number through telephone lines and send some DTMF frequently through the telephone line to the dialed number with a microcontroller. Is there any single chip telephone IC available which can be easily interfaced with arduino, just like the old dial up modem which i can dial number from a PC. Help me to get the simplest and cost effective way to do this.

Thank You Prem

There is an Arduino phone connection tutorial here

The DAA is about $15 from ebay,, and the DTMF generator is very cheap

I am trying to build one myself so I can't guarantee anything, but this looks like your best bet.

Here is a video overview of his project:

The below listing is a nice module that contains all the DDA and DTMF hardware required and would let you just concentrate on your sketch software development. Interfacing with telco lines is not as simple as it might appear, keeping in mind when the line gets rung by an external caller there is 90vac applied on the line! Also most telco laws require an FCC approved DDA to wire an external device to a phone line.


I am building a system where I have a “virtual” telephone line powered by a 9 volt battery and a telephone at one end and the arduino at the other. How does this DAA/DTMF combo chip hook up to an arduino does it use I2C, Serial, SPI, etc.? Could I just follow the instructions at this post ( and hook is up differently on different pins?