The 74HC157; 74HCT157 is a quad 2-input multiplexer. The device features select (S) and enable E inputs. A HIGH on S selects data source 1, a LOW data source 0. A HIGH on E forces all the outputs (1Y to 4Y) LOW. Inputs include clamp diodes. This enables the use of current limiting resistors to interface inputs to voltages in excess of VCC.