A 555 timer in a monostable multivibrator configuration generates a single output pulse of fixed duration in response to a trigger input. In this setup, the 555 is wired so that its output is normally low. When a negative trigger pulse is applied to the trigger pin, the output goes high for a time interval determined by an external resistor and capacitor (T = 1.1 × R × C). After this interval, the output automatically returns to low, ready for the next trigger. This circuit is commonly used for timers, pulse generation, and switch debouncing applications.
