How does DTMF generator work?

sweet_nth · Mar 29, 2005

Hi,
im trying to do a project where it requires auto dialing, i.e. to dial a specific number when triggered to do so.

well, my teacher suggested i recorde the number (sound of numbers) i want to dial on a record/playback chip and play it when its time to call, but i dont know where to play it??

my question is: i know that each number has a diff. frecuency, but how does the sound get through? is it through the DTMF? and if so, can i just play a pre-recorded dialed numbers and that would work??

the phone i took apart has this IC UTC2411, and i searched the net for a data sheet, but all i got is wholesale lists for that IC.. anyone knows a good online source for IC's data sheets ? or any other source?

i thought that this should be easy, but it isnt as easy as i thought. please help!!
thank you

glenjoy · Mar 29, 2005

DTMF question

Get a voice recorder, and record the tone of the phone via the handset's speaker. Try to dial a number and record it.

After recording, hook-on the telephone and hook off it, then play the recorded phone number at the handset's microphone, there it will call the number.

viveklengade · Mar 29, 2005

Re: DTMF question

i have used one voice rom ic where i can store 8 diffrent voice. try to record u r tone on to that. tht ic having 8 trigger pins trigger which u want and dial yhe no.

by the way wht is u r application.

ppenday · Mar 29, 2005

Re: DTMF question

u can find good datasheets on national semiconductor website

C-Man · Mar 29, 2005

Re: DTMF question

@sweet_nth,

everything can be done using a microcontroller and a PWM output

See my post here for details:

best regards

sweet_nth · Mar 29, 2005

Re: DTMF question

Thank u all,
all ur replies are greatly appreciated and important

my application is a device u leave with baby-sitter and it calls u when the baby has been crying for a continous 3 minutes non-stop..

i might have more questions in the future

i will try ur hints, thanks

Added after 4 minutes:

glenjoy,

i have tried this earlier, i got a disconnected phone, and i pressed the numbers i want to call to the connected phone microphone ( the disconnected phone has a loud sound key pad) and it didnt work, do u think because the sound wasnt loud enough, or it was noisy? what do u mean by " hook-on the telephone and hook off it" .. do i need to do something to the phone before i start the recorder?

shafee001 · Mar 29, 2005

Re: DTMF question

try to use dtmf generator

5089

hm_fa_da · Mar 29, 2005

Re: DTMF question

hi ;

if you are using Microcontroller you can use a DTMF generator like MT8870 ( i have used it )

you can finde many datasheets in www.datasheetarchive.com
and www.alldatasheet.com

regards.

jojokatada · Mar 29, 2005

Re: DTMF question

C-Man said:
@sweet_nth,

everything can be done using a microcontroller and a PWM output

See my post here for details:
h**p://

best regards

the link from resonas application note no longer available
could you upload it
appreciate

Bingo600 · Mar 29, 2005

DTMF question

A search on the reneseas site with keyword dtmf revealed this

http://documentation.renesas.com/eng/products/mpumcu/apn/dtmf.pdf

And lots of other good info

/Bingo

masud58 · Mar 30, 2005

Re: DTMF question

U may use FAX Modem to dial ur desired number. u must link 8051 to modem which ini modem then dial number.

masud
matrix electronics
dhaka
bangladesh

gidimiz · Mar 30, 2005

Re: DTMF question

Hi sweet_nth,

I think avery one missed the point that you have no idea how DTMF works.
The best way to start is doing a search in google for how dtmf works
Here is the first link that came up:
http://www.genave.com/dtmf.htm

I think going about recording a DTMF and then palying it, is not a good idea. When you puild a project you have to remember few rolles:
1. Will it work for a long time, or will i have problems...
2. How hard is it to the user to configure it...
3. How cost effective is it? i.e. how may parts do i need...
and so on.

taking this 3 questions that are mostly important for your project, i would say that using a micro is the best soulution. It can do all of what you need. With a MIC you can hear the baby crying for 3 minuts, and then dial to what ever numver you need.

There is nother way, that a company is saling there product. They are using a DTMF generator and a voice recorder IC and a small MCU. They can dail any number that you pre-programed and also recored your voice, lets say " baby is crying for 3 minuts". Then when the micro receives the triger it calles, and then plays the message.

Now after you understand how it works, you can do another search in google for designes with DTMF. +dtmf project circuits

If you found my answer useful, click on the button that says Helped me. ( NO points will be taken from you! )

Good luck.

kamejoko80 · Mar 31, 2005

Re: DTMF question

I used the Tone Generator co make the DTMF signal , this sort quite cool that can make .wav files for DTMF.
you can download the program from
https://www.nch.com.au/tonegen/

And decoded the DTMF signal, I used the PC ang it own sound card.
Transmit a tone number :
It's very simple that we play back the .wav file of this telephone number, the file are generated by the Tone Generator program. For example, if we transmit some digist 1-2-3-4 we play back the .wav files digit1.wav-digit2.wav-digit3.wav-digit4.wav in the sequence of numbers.
To recieve and decode the DTMF signal :
I used the Goertzel algorithm, you can get some imformation about this filter by searching from google web site. And I wrote my own program for demonstration.
We can get the DTMF signal via Mic In or Line In of the sound card (see my program code, I wrote it by using Visual Basic tool). Think ! A MCU with a ADC can replace the PC and sound card can operate properly ???

kamejoko80 · Mar 31, 2005

Re: DTMF question

Sorry , I've uploaded a wrong file

sweet_nth · Apr 1, 2005

Re: DTMF question

well,
ty all,, but i dont have alot of time, (less than 2 weeks), ive decided to use the phone circuit that i have and simply push the redial button, the reason im doing that is i will need to work on recognizing the baby crying sound,,

wish me luckkkkkk

Jack// ani · Apr 2, 2005

DTMF question

Just a curious question......Do dialup modems have DTMF recievers?? Is it possible to detect caller's phone number using this reciever? I want to know how these tones are send by the telco, do they send the callers phone no before the ring or after it???

masud58 · Apr 2, 2005

Re: DTMF question

Some Day Ago I am working with fax modem and at89s8252 . which dialed one or more phone number or another modem linking data tranfer each other with terminal .
if u insist then i can send this keil asm and hardware design.

Another questen.
what is point , and why i am junior label ? tell me elektroda!!!!!!!!!!

Thanks
Masud

sweet_nth · Apr 2, 2005

Re: DTMF question

Jack// ani said:
Just a curious question......Do dialup modems have DTMF recievers?? Is it possible to detect caller's phone number using this reciever? I want to know how these tones are send by the telco, do they send the callers phone no before the ring or after it???

i dont think i totally understand ur question,,, but see if these links help ..

**broken link removed**
**broken link removed**
https://www.sandman.com/digit.html

its just some products out there that uses DTMF to detect dialed phone numbers,

shafee001 · Apr 2, 2005

DTMF question

yes fax modems have it's own reciever, and they can detect caller ID, like USRobotics,
telecomm sends caller ID after 1st ring and before the second, so there is a little long scielnce between 1st and 2nd rings

Jack// ani · Apr 3, 2005

Re: DTMF question

shafee001 said:
so there is a little long scielnce between 1st and 2nd rings

Oh...yes I have noticed it but never understood the real reason!

Thanks

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