The 555 monostable timer circuit is commonly used when a one-shot pulse of up to a minute or so is desired as initiated by an input trigger.
In some designs, particularly battery operated circuits, it is desirable that the circuit use no power when not triggered and the circuit is quiescent.
Discussed here is a modification of a typical 555 one-shot circuit that uses a couple of transistors to remove the power when the one-shot output is over.
An added bonus is that these transistors also...