really need help on PWM and PPM circuit...

[nasuha]

hello everyone..im need some helps...

i've construct the PWM and PPM circuit...the output going smoothly...

but i've some problem...im not very understand about the circuit..

i got the circuit from internet and it doesn't explain in detail

For PWM, A1 is astable multivibrator and A2 is monostable..thats all i know..

i have no idea about the PPM circuit...

can anyone help me to understand the circuit?..

thank you soo much!