• Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

DTMF Decorder & 8870 Chips

Status
Not open for further replies.

lee_man_tbu

New Member
I was wondering if anyone had any idea's on how too intergrate a DTMF decorder with a microcontroller.

The application i am using this for is, too have a PIC MCU control a secured enterance on an apartment building and i want the PIC too call through existing phones too each suite. Once the call is received, the tentant can hit the # key too let the user in. I have all the other ends of this project underway, just the intergration of the DTMF circuit is giving me some trouble.

Anyway help would be great.
 

John P

New Member
I've used the Teltone M-8870. As I recall it was very easy. You get 5 output bits, 4 of them with a digital code telling you the button that's pressed, and a 5th that goes high when any button is activated. You just get the processor to monitor this and read the 4-bit code when needed. There's also an output enable line for the 4 identity bits but you can leave this enabled all the time if you want. The chip's oscillator runs off a TV colorburst crystal (3.579545MHz).
 

lee_man_tbu

New Member
DTMF Circuits

I just have a few other quick questions and though maybe you could help me out with them that would be great.

First, that Chip you were talking about the Teltone M-8870, is this a TTL or CMOS IC? if so, how did you handle the high Voltage from the phone lines? Optoisolaters possibly?
Next, you said there was 5 Output Pins on this chip, 4 of which being data, can i use this chip too send Singals aswell?
I will tell you why, for my appliacation, i am not worried about receiving Keytones(Just one Keys at the Most), but i need my system too be albe too dial a Phone number, the user too Answer and then Press a Key and this will come back too the pic which will open a door.
Any details you would have on connecting the phone line too The M-8870 too phone lines or if you know where i can find a datasheet for this chip would be great

Thanks

lee_man_tbu
 
Status
Not open for further replies.

Latest threads

EE World Online Articles

Loading
Top