does you specification say you have to use a 555IC and analogue switch?
You could use a microcontroller to do both the modulation and demodulation - what bit rate are you working at?
no, there is no target systems... i have to show the output wave form on the CRO..
both modulated and demodulated ..
data=1khz (o/p of the astable multivibrator)
carrier frequency = 5khz (sine wave)
the 0 and 1 must be generated using a 555 timer in the astable mode , the is the input to the analog switch where the modulation is take place..