The KK74ACT158 is identical in pinout to the LS/ALS138, HC/HCT138. The KK74ACT158 may be used as a level converter for interfacing TTL or NMOS outputs to High Speed CMOS inputs. This device routes 2 nibbles (A or B) to a single port (Y) as determined by the Select input. The data is presented at the outputs in invertered form. A high level on the Output Enable input sets all four Y outputs to a high level.