Re: telephone circuit
- From: "Stephen J. Rush" <sjrush@xxxxxxxxxxx>
- Date: Wed, 03 Sep 2008 01:41:42 -0500
On Tue, 02 Sep 2008 12:16:36 -0700, lerameur wrote:
Hello,
I am using a pic controller for a dialer project. My goal is to dial a
number, when the receiving end picks up, then send some dtmf tone for a
few minutes.
Sounds simple, but I do not know how to tell my controller that the
receiving end has picked up or not. Right now I just let it ring for 10
seconds, and send my dial tone after that. I would like it to be more
'intelligent' by knowing when the receiver has picked up so I can send
the dial tone (message),
When the central office connects to the called phone, it sends the 20-Hz
100-volt ring signal to that phone and a tone-burst signal called the
ringback to you. When someone making a call says he "hears it ringing",
he's referring to the ringback. I don't remember offhand the two
frequencies involved, but a little Googling will find them. Send the
DTMF dial string, then wait for the ringback. Measure the time between
tone bursts, because it may vary between central offices. If that much
time elapses without a ringback burst, you know the other end has gone
off-hook. To be safe, you also need to detect the error conditions: a
busy signal or complex audio that doesn't sound like the ringback or busy
tones. That will be one of the call-not-completed voice messages.
.
- References:
- telephone circuit
- From: lerameur
- telephone circuit
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