The 74HC221D is a dual non-retriggerable monostable Multivibrator with reset is a 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 Multivibrator are dual non-retriggerable monostable multivibrators. Each multivibrator features an active low-going edge input (nA) and an active high-going edge input (nB), either of which can be used as an enable input. Pulse triggering occurs at a particular voltage level and is not directly related to the transition time of the input pulse. Schmitt-trigger input circuitry for the nB inputs allow jitter-free triggering from inputs with slow transition rates, providing the circuit with excellent noise immunity. Once triggered, the outputs (nQ, nQ) are independent of further transitions of nA and nB inputs and are a function of the timing components.