These monolithic data selectors/multiplexers contain inverters and drivers
to supply full on-chip data selection to the four output gates. A separate
strobe input is provided. A 4-bit word is selected from one of two sources
and is routed to the four outputs. The ’157, ’LS157, and ’S157 present true data whereas the ’LS158 and ’S158 present inverted data to minimize propagation delay time.