Sound Recognition [ Solved ]

Actually that is best done with hardware combined with software, and something like this is already done...
It's called a PBX system or TalkSwitch, here's the first web-site I found on this: http://www.talkswitch.com/

It cannot be done only through software (sound) because there are signals that go through the phone line that don't make any sound.
For example the hold button, lets say you talk on the phone and you put it on hold, the software program will detect no sound, therefore it will assume the call was ended. Especially if you want to time it to the second, with sound detection only it's imposible.

All you can do with sound detection is to make an aproximate, so the time will be off from what your phone company will tell you.


Here's what I used this for:
At my work we do customer service (not me though, I'm the IT guy there).
When a customer calls I made a Caller ID (phone number taken from modem) and it's displaied on my client program that they use. They double click on the phone number (when the customer calls), and they can see customer history, by the time customer service picks up the phone they already have the customer information on the display. Also, we record the conversations (to MP3), obviously we tell the customer that we do record the conversation.

Now the problem is that when WE call the customer, we don't have Caller ID, so in order to get the customer information you would have to type in the computer the phone number you are dialing on the phone.
That's how i came up with this idea. I made the program as soon as you pick up the handset, it will detect the beginning on the call (dial tone), then when you start dialing, it will display on the screen LIVE, the buttons you press on the phone. When it detects the ring, then it knows that we dialed all the numbers, and that's the complete phone number.

Unfortunatelly our best csr left us, and we are left with a dumb *blip* that does not know how to use the features in the program, so I gave up perfecting this, and eventually I took the feature off the program.

Excellent circuit !!!
I know electronics, but I have 4 questions :mike:

1) Your are using a Zenner for the 5.5V circuit, right ? Can I use 12V, i have a transf. ready ...

2) What uis the vertical line after MIC OUT ?

3) Do you have a replacement for the MPS A44 ? (more easy to find in Brazil)
BC338 NPN Silicon 800mA 25-Volts

4) The tranfs. before MIC OUT is one of those isolation transf. 1:1 ?

Thanks !!!

BTW. you can use it for Skype. How about that ? :bigyello:

1) I attached a schematic of how it would be if you put a 12V zenner, but all the rezistors are aproximated. I did not know what tranzistors to use, use whaver you want, I don't think it matters, as long as they are powerfull enough. The recording circuit uses VERY little power, so the tranzistors don't have to be that powerfull.

2) The vertical line I pu it there to show that there are 2 separate circuits.
If you want the output to be for microphone, then use only the left side of the circuit (wich does not need power). But if you want to plug it in the auxiliary jack in the computer, then use the whole circuit.

3) I think you can use any tranzistor for this circuit, the transistors I used are not even ment for sound :) and it still works... it's a simple circuit, so anything close to what I have should be good enough.

4) The transformer I don't have any specs for it, all I know is that it has 100 ohms on input and output i.e. 1:1, but I don't think you should use a transformer that is less than 100 ohms, greater is better.


I don't see how you would use this for Skype, Skype is all software, nothing to do with hardware...

Thanks for the quick response.
I'll use the complete circuit then .beuase I want to ive audio back to the phone line also.

Skype --> I am using my cordless phone on Skype. Skype recognizes DMTF tones and dials. I answer calls on the phone, etc ..
I was using a circuit that doesnt separate Audio In and Out, so there is some echo (the other person hears himself because the line is just isolated )
With your circuit, looks like it separates the Auidio In from Out and thats great !

Thanks !

Martin

Tone Detection and Generation is usefull on PC connected to scanners or Radio or R/T sets, esp. for Amateur Radio.

There are about 50 CTCSS tones from 67Hz to 250Hz. Motorola calls thes "PL Tone"

There are 16 DTMF tones used, not just twelve. Used to control remote equipment by radio. Google on IRLP too.

Tone bursts such as 1750Hz

Also DCS is probabily tone based codes.

Hotwind Software www.tapiex.com does rather over priced .dll libraries that work in VB for playback, recording, FFT, tone generation and tone detection. But at about $600 I think it is overpriced. Easy to use "streaming" live from sound card to detect DTMF though.