I want to build a pulse generator myself, and I have search the website find a simple construction of generator. But I can not understand this circuit. Can someone help me? Furthermore, if u have some other idea please tell me. Thank you.

 

U2-1 is a fairly clever oscillator - I would never have come up with something like that. Whenever the output is lower than the potentiameter setting, the output will be driven high. Whenever the output is higher than the potentiameter setting, the output will be driven low.

U1-1 is an integrator of some sort, using Q1 as the sampling switch, but I must leave to those more learned than I the mysteries of of it's operation.

U1-2 is a comparator with fixed reference level.

U2-2 is a comparator with variable reference level, allowing manual adjustment of pulse width.