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PICList Thread
'Telephone Fax Calls Detection'
1997\01\06@155318 by ciao

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does anybody know some *simple* circuit (PIC based?)
to recognize incoming fax telephone calls and activate a line switch??

thanks all in advance!!

1997\01\06@163106 by Christopher Zguris

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At 09:51 PM 1/6/97 -0800, you wrote:
>does anybody know some *simple* circuit (PIC based?)
>to recognize incoming fax telephone calls and activate a line switch??
>
>thanks all in advance!!
>
>

The thing I never understood about those fax switches is how they get the
fax to pickup. The line rings, your answering machine picks up, the switcher
detects the fax tones and connects the fax machine. But the fax won't pick
up _unless_ the line rings!

Do the higher-end switchers include a ring generator circuit (not
complicated, they're commercially available) that rings the fax to make it
pick up? I played with a cheapo switcher, and it drove me nuts. Every time
I've tried to fax to a voice/fax number that uses a switcher I've always had
the human pick up and say "hello", so I don't think the switchers _are_ working.

Personally, I'd go for distinctive ring. I'm sure it'd be a simple thing for
PIC to "listen" to the incoming ring and - if it's "line 1" (voice) -
physically disconnect the fax, or if it's "line 2" (fax) disconnect the
phone. The line connected would still be ringing, so it would trigger a
phone, answering machine, or fax without any problems.

Hello Direct also sells a one-line distinctive ring switcher for ~$50, and
monthly service here in the US only costs a few dollars a month.

Chris
(answering a _different_ question, I think)

   ======================================================================
         Christopher Zguris  -  spam_OUTczgurisTakeThisOuTspaminterport.net  -  Uhhh, Ear?
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                                 BUREAUCRACY
                                 ===========
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     them and when you can milk them.  Then it pays you not to milk them.
   Then it takes both, shoots one, milks the other and pours the milk down
     the drain. Then it requires you to fill out forms accounting for the
                                missing cows.
   ======================================================================

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