Are you using a transformer between your decoder and the phone line?

	


On 14 Sep 2007 at 22:15, mamad876 wrote:

> 
> Hi all,
> 
> Recently I made a Caller ID decoder using SM8223 chip and I decided to
> connect it's out put to computer serial port and I bought a MAX232 chip and
> I made a prototype board regarding to it's data sheet.
> My problem is when I use my decoder separately it works well (I think
> because actually I don't see the result but I can see the CID found signal
> with an LED connected to board) but just when I connect ANY PINS of my RS232
> converter to the CID board (Even GND wire of my RS232 Pro board) it stops
> working (ie. LED doesn't show CID signal ). I tried to separate the Power
> supply of my boards but this time the same problem when connecting TxD (ie
> T1 pin) of MAX232 to CID decoder serial output was exists.
> 

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