Dual retriggerable monostable multivibrator with reset, The 74HC123, 74HCT123 are high-speed Si-gate CMOS devices and are pin compatible with Low-power Schottky TTL (LSTTL). They are specified in compliance with JEDEC standard no. 7A. The 74HC123, 74HCT123 are dual retriggerable monostable multivibrators with output pulse width control by three methods, The basic pulse is programmed by selection of an external resistor (REXT) and capacitor (CEXT). Once triggered, the basic output pulse width may be extended by retriggering the gated active LOW-going edge input (nA) or the active HIGH-going edge input (nB).

DC triggered from active HIGH or active LOW inputs
Retriggerable for very long pulses up to 100 % duty factor
Direct reset terminates output pulse
Schmitt-trigger action on all inputs except for the reset input