How to Interface DTMF generator with Telephone Line

vik1501 said:

Kinjalgp

How do I download schematic ? I am using a transformer typically found in epabx system. I am using 0.1uF cap in series with coil winding as follows. I have tried to put this in following format. I hope u understand !!

Can u suggest some tools ?

(GND)
------[100k]----[100k]----(VCC)
|
|_________________+ of LM324<3>
tone signal <1> tip
fr mt8888 ------coil xf --[0.1uF]---
----------->[ 0.1uF ]----> [ 1k ] __- of LM324<2> | () ()
| | () ()
| | () ()
----[var 47K]---------- |GND ------ring

( Amplifier using LM324 )

0.1uf is used to isolate dc level on either side. Non inverting i/p is provided with voltage divider to set dc voltage at 2.5V.

Gain is adjustable


I did some jugglery as above :? and tried to see the numbers on caller id device. The nos are displayed incorrectly. Nos 8,9,1,5 are not seen at all when i tried to send tone sequence 012345678901... on line

Regards & thanks

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vik1501 said:

Oh ! I did it !!

The problem was one port pin of microcontroller was bad. It was remaining at VCC level all the time. Hence wrong o/p from dtmf generator. :shock:

Thanks to all those who kept scratching their heads....Now no need to do that friends !!!

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19fa952 said:

hi
i have same problem please send for me schematic if it is possible
thank

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phalanx said:

19fa952 said:

hi
i have same problem please send for me schematic if it is possible
thank

Click to expand...

Is that an offer or a request? :lol:

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