autoanswer telephone line

hi how is it possibile to wait for some rings and then activate the line to capture DTMF signals ? thank you

Reply to
merco
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Yes.

Reply to
OBones

well, i see... but i asked "how" ?

OBones ha scritto:

Reply to
merco

I know, hence why I canceled the message, I missed the "how" part.

Detecting rings is done with a RC network across the line, like on this schematic with R7/C3 (bottom right)

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On this one, you get an optocoupler in the path to interface with low level voltage (12V) logic.

To activate the line, I think it's enough to put a resistor across it but can't remember the exact value. And detecting DTMF tones can be done with an MT8870 like on this schematic:

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Hope this helps.

Reply to
OBones

thanks, the problem i have is how to pick up the line... maybe a 600 ohm resistor ?

OB> > well, i see...

Reply to
merco

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Yes, that will work.

The second problem is that you\'re top posting.  Please bottom post.
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Reply to
John Fields

You need several circuits.

a. Ring detect circuit

b. Something to count the rings before answer

c. something to loop line and draw loop current from line/telephone exchange

d. something to couple the audio after looping

e. something to decode the dtmf

f. something to hangup.

JG

Reply to
Joe G (Home)

By using a ring detector, a DTMF receiver and a microcontroller.

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Reply to
Nico Coesel

You mean an "infinity bug"?

Michael

Reply to
Michael Black

Hack an ordinary answering machine?

Good Luck! Rich

Reply to
Rich Grise

a ring detector, monostable, counter, relay, line transfromer, DTMF decoder...

or use a modem. many V90 modems will decode DTMF if you ask them nicely.

Bye. Jasen

Reply to
jasen

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