View Full Version : DTMF

06-17-2008, 08:46 PM
hi guys,
i'm quite new to robotics....i want to make a DTMF controlled bot....but i dont know how to get the DTMF tones from my phone....please help

06-18-2008, 07:52 AM
@rishvanth: Welcome to Robotics India :).

You could start making your bot with a Exar XR2211 IC. These are really cheap (~Rs.25-45). See the datasheet to see how you can interface it with your uC. You may need to use the XR2206 IC (Function Generator IC), as a tone generator. I have seen people design an FSK Modem for *only* recieving DTMF tones without a tone generator, but it depends entirely on the type of handset that you use. Normally a tone acts as a 20V power supply for the phone, and without it, the phone cannot generate a DTMF signal.

If you PM me, and are a little patient for some time, I may be able to dig out some old designs that I made for a RS-232 based Modem using an XR2211, XR2206, AT89C2051 and a MAX232. That may help you.



06-18-2008, 12:09 PM
XR22xx chips are obsolete and not available.
There are dedicated DTMF ICs available cheap and everywhere. Google for DTMF IC.
Take the o/p from the earpiece of the Telephone to an audio amplifier.

Cordless phones are easy to use....!!
I still have a Cordless 'base station' running around the house, controlled by the 'handset'. It was a 1990 student project made by my students at school.