Integrated Circuits Used 74LS138 74LS04 Procedure Add IC 74LS138 into ICBase-2 (74LS138).Connect VCC Port to Pin-20 (VCC) of ICBase-2 (74LS138).Connect GND Port to Pin-8 (Ground) of ICBase-2 (74LS138).Add IC 74LS04 into ICBase-3 (74LS04).