Telephony

Homer J Simpson escreveu:

I live in Brazil, so I would like a circuit connected to my telephone line to disconnect my dial-up connection. I would like to get the fixed telephony world-wide standards.

thanks you, PH

Is that legal in Brazil? Do you have call waiting?

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Hmmm...  Wouldn\'t it make sense, since you live in Brazil, to get
the standards for your country?

Yes, I have the service.

Forgive me:

Yes, I have the call waiting service installed. I think it is legal in Brazil. It isn't a problem anyway :-) Isn't legal in US?

They are alike, I believe. I would like to read the US and europe standards to get some ideas. I could not to get the brazilian standards yet. Only for mobile communication :-(

And what about the circuit? Do you think it possible?

thanks you, PH

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It may not be necessary if you can configure your modem to
disconnect on call waiting:

http://www.modemsite.com/56k/v92.asp

here\'s a link to get you started:

http://en.wikipedia.org/wiki/Call_waiting

with much more available at:

http://www.google.com/search?sourceid=navclient&aq=t&ie=UTF-8&rls=GFRC,GFRC:2006-50,GFRC:en&q=Call+waiting

Thanks you by the links but I would like to make a circuit to detect the call waiting tone and disconnect my dial-up automatically [answering the call waiting tone with the FLASH + 1 in Brazil to accept the incoming call and disconnect the current call] independent if my modem and my telephone company supports v.92.

regards, Pedro Henrique

--- From:

It appears your call waiting standard is:

call waiting = 425/50,0/1000,

which means 425Hz for 50 milliseconds followed by 0Hz for 1000 milliseconds.

That means you'll need to detect the 425Hz tone for long enough to determine whether it's valid or not and then detect the absence of that tone for 1 second in the presence of your data signal. You may want to do that two or three times just to make sure it's really the call-waiting signal, then generate the FLASH +1 signal to disconnect the modem and transfer the call to the phone.

-- JF

Very thanks by informations. Only Today I could read in a book today that in Brazil these informations:

425 Hz during 60 ms =B1 10% 0 Hz during 250 ms =B1 10%

JF,

I was thinking in a simpler solution: to install a 425 Hz filter in my phone and connect to a loudspeaker. So I will be able to hear the signal and go to telephone to press FLASH and 1. What do you think? There is a telephone connected to modem, so it will not be a discomfort to me. Could you give me a suggestion to the filter?

thanks you!, PH

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Yes.  I think the right filter would be basically a squelch  that
would use an averaging detector for the data and then  use the
filtered 425Hz rising above that level to open up a gate and let the
425Hz through.  Either that or use the 425Hz signal to turn on a
beeper, momentarily, to let you know that someone was trying to call
you.  That might be the better way because it would get rid of the
annoying squelch tails.
 

Or, maybe, something like this:

http://phonetray.traysoft.com/?gclid=CMDFg_fGnYoCFQgTWAodkTi2nA

If it\'ll work with your modem. 

You can download it for free to find out, anyway.

I\'m interested in the filter, so I\'ll work up something tomorrow and
post it probably on Friday, unless something unexpected comes up.

I don't believe, that softwares works! Very very thanks, JF!

Anyway, I am also very interested in others solutions like a filter/ loudspeaker or better, a digital circuit with a LM567. This CI isn't very expensive.

Very thanks, Pedro Henrique

The secret of that software is only to add string modem "+PCW=3D0" or "+PCW=3D1", no?

---- Portuguese - Brazil - for documentation Para se desconectar uma conex=E3o dial-up ativa automaticamente quando h=E1 algu=E9m tentando chamar o respectivo n=FAmero telef=F4nico, adicione a string +PCW=3D1 ao modem. =C9 claro, o servi=E7o Chamada em espera deve estar ativo na linha telef=F4nica.

--

Very thanks,
Pedro Henrique

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I don\'t know.  Try it.

I tried and it has worked.

PH

--- "Integrated Circuit" (IC), no?

Good thought.

Since your call-waiting tone is 425Hz, one cycle takes:

1 t = ------- = 0.00235 seconds 425Hz

to complete, and since the tone will be on for 60 milliseconds, the number of cycles during that time will be:

60ms n = --------- = 25.53 ~ 25 2.35ms

Looking at the data sheet for the 567:

on page 5 (407) there are two graphs which show frequency VS bandwidth and greatest number of cycles needed for output. Since you have 25 cycles available it looks like if you set your bandwidth for something between 10 and 14% it might work. I don't know what effect the data signal is going to have on the 425Hz tone other that it'll degrade its detection, so the best thing might be to just wire one up and see what you can do with it.

-- JF

--
Excellent!

So now you don\'t need the filter?

No matter, I\'m intrigued so I\'ll work something up and post what I
find when I\'m done. :-)

Well, I don't need the filter, but I don't have nothing to do and I'm intrigued too :-) .

I am plus interesed in tone decoder. The problem is that input to LM567 is at most 200mVrms, so I will need to make a reliable conversion and protection for the CI.

PH