> Also can somebody tell me what kind of modulation an IR-signal uses ??
> (IR-signal ---> I mean the IR-standard of Sony : SIRCS !) I know they use
> pulse-width coding :
[...]
> So, you get a signal containing pulses with a different width !! I want to
> know what form of modulation this is ?? (Think is fase modulation, but don't
> know why ?)

It's a form of Pulse Width Modulation (PWM).  However, it is not the kind of
PWM that is normally produced by PWM peripherals on microcontrollers.
Those usually vary the pulse width but keep the frequency constant, whereas
the Sony SIRCS varies the pulse with but keeps the "gap" time constant.

There's some PIC code to generate SIRCS on my web site at
        http://www.brouhaha.com/~eric/pic/controls.html

And, if you need to receive SIRCS, there are links on that page to a
PIC16C84-based receiver project by Prashant Bhandry.