The HD74LV123A features output pulse-duration control by three methods. In the first method, the A input is low and the B input goes high. In the second method, the B input is high and the A input goes low. In the third method, the A input is low, the B input is high, and the clear (CLR) input goes high. The basic pulse duration is programmed by selecting external resistance and capacitance values. The external timing capacitor must be connected between Cext and Rext/Cext (positive) and an external resistor connected between Rext/Cext and Vcc To obtain variable pulse durations, connect an external variable resistance between Rext/Cext and Vcc. Once triggered, the basic pulse duration can be extended by retriggering the gated low-level-active (A) or high-level-active (B) input. Pulse duration can be reduced by taking CLR low.