The CD4093B consists of four Schmitt-trigger circuits. Each circuit functions as a 2-input NAND gate with Schmitt-trigger action on both inputs. The gate switches at different points for positive and negative-going signals.
CD4093 - Quad 2-Input NAND Schmitt Trigger
The difference be-tween the positive (VTa) and the negative voltage (VTb)isdefined as hysteresis voltage (VH). All outputs have equal source and sink currents and con-form to standard B-series output drive.
CD4093 is a very useful chip, as it has a Schmitt-trigger and it is a nand, cmos, low power. It can be even made to function like an amp in some configurations. It was used in debouncing circuits, oscillator circuits and input signal conditioning of digital circuits.
DMM range and AC-DC mode Logic
If you had a train of square pulses from a magnetic sensor or proximity sensor. You could use this as a monostable or singleshot to reject noise and get a clean square wave from a messy input.