The 74HC123 and 74HCT123 are high-speed Si-gate CMOS devices and are pin compatible with Low-power Schottky TTL (LSTTL). The 74HC123; 74HCT123 are dual retriggerable monostable multivibrators with output pulse width control
The DM74LS123 is a dual retriggerable monostable multi-vibrator capable of generating output pulses from a few nano-seconds to extremely long duration up to 100% duty cycle. Each device has three inputs permitting the choice of either leading edge or trailing edge triggering.
74LS123 and 74HC123 features