DTMF decoder, please help!!

[mindctrl]

Hi everybody

I need a little help. I want to build a circuit that I can connect directly into a phone cord, and then it detects and decodes DTMF sounds and outputs them to a PIC for display on an LCD. Before you even ask, no, I'm not building this for call logging or spying on anybody.

Actually, I plan to build something like the portable rotary phone, but first I need to figure out how to detect DTMF tones before I can feed them to the cell phone module (which uses standardized ATD commands).. Any help on this is appreciated as always!! If you know about a DTMF decoder module or can offer some advice/criticism, please do. Thanks everybody.

--mindctrl

 

[tusharg]

DTMF Decoder MT8870D

You can use MT8870D from Mitel. I had used it for my project. Don't know if it's still available.

 

[stevez]

Amateur radio operators use DTMF codes for remote control on many bands including VHF and UHF. I would expect that you'd find considerable information by looking thru amateur radio references - if you're not able to find what you need otherwise.

 

[evandude]

if you're using a rotary phone, you're not going to get DTMF tones... (unless it's a newer, "retro" electronic one that just LOOKS like a true old rotary...)

rotary phones used pulse dialing, because that's what the mechanism generated (more pulses the more you turned the dial before releasing... corresponding to the numbers on the dial...)

have you checked out the sparkfun rotary cell phone project?
(they are generally regarded as the pioneers of the idea) they have pretty good detail about the construction, should be more than enough to build your own...
**broken link removed**