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?

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

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:

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

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.

I tried and it has worked.

PH

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

Good thought.

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

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

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

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