At 07:12 AM 10/1/00 +0000, you wrote:
>hi, i will be doing a tele remote system. at the moment i am thinking of
>using those readily available DTMF generator or receiver IC.
>My question is, can a PIC alone be able to generate those signal( w/o other
>IC )?

Yes, but you may have an easier time if you use the holtek DTMF transciever
chips.



>Since i am very weak in analog electronics any information on
>interfacing the telephone line will be greatly appreciated.
>for example, what kind of impedances that is neccesary to be seen by the
>telephone exchange when it is on hook of off hook? i read that it is around
>220ohm. can i simply use a resistor to match the required impedance? or can
>anyone tell me what does a 1:1 transformer that are normally found in modem
>used for? I would like to learn more about impedance matching in a
>communication line, can anyone point me to a good and practical tutorial?


Grab a copy of "Understanding telephone electronics" from radio shack.
To do a proper line interface isn't hard, but it's not something you just
throw together.



>sorry for being too [EE]: , thanks a lot.
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