Which TTL IC device has two thresholds to improve level switching speed?

The TTL IC device that has two thresholds to improve level switching speed is the 74LS14, which is a Schmitt Trigger inverter. This device features a hysteresis effect that provides two distinct voltage levels for switching, allowing for faster transitions and improved noise immunity compared to standard TTL inverters. The Schmitt Trigger design helps minimize the effects of signal bounce and ensures cleaner signal propagation.