The 555 isn’t just an oscillator, though. It can also be used in monostable (one-shot) mode, producing a fixed output pulse width in response to a low-going signal on the TRIGger input.

The 555 timer is used as a free running oscillator. We know that this not be very stable when compared to even the worst of crystal oscillators, but that’s what makes it work so well as a random ...