The NE555, SA555, and SE555 monolithic timingcircuits are highly stable controllers capable ofproducing accurate time delays or oscillation. Inthe time delay mode of operation, the time isprecisely controlled by one external resistor andcapacitor. For a stable operation as an oscillator,the free running frequency and the duty cycle areboth accurately controlled with two externalresistors and one capacitor.The circuit may be triggered and reset on fallingwaveforms, and the output structure can sourceor sink up to 200 mA.