How to Interface DTMF generator with Telephone Line

[vik1501]

Dear friends,

I have build a dtmf generator and want to i/f that with telephone line for autodialing.

Can anybody show me the way out ? :roll:

 

[kinjalgp]

Can you show us your schematic?

In most cases it is done using 1:1 (600 Ohm) phone coupling transformer.

 

[vik1501]

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

 

[vik1501]

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

 

[vik1501]

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 !!!

 

[ljcox]

I do the drawings that I post in PowerPoint. You save them initially as a .ppt and, when ready to post, Save as a .gif. There are various options in the "Save as" window one of which is .gif.

Len

 

[19fa952]

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

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 !!!

 

[phalanx]

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

Is that an offer or a request? :lol:

 

[19fa952]

Dear friend :wink:
it is request!

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

Is that an offer or a request? :lol:

 

[Raz00]

Hey i have the same problem could anybody send me the schematic to interface to the telephone line . im using a pic16f84a and dtmf generator Tp5088 ??????