The CD74AC257, CD74ACT257 and CD74ACT258 are quad 2-input multiplexers with three-state outputs that utilize the Harris Advanced CMOS Logic technology. Each of these devices selects four bits of data from two sources under the control of a common Select input (S). The Output Enable (OE) is active LOW. When OE is HIGH, all of the outputs (Y or Y) are in the high-impedance state regardless of all other input conditions.