Integrated Circuits Used 74LS21 74LS04 Procedure Connect Output-13 to Pin-2 (Output) of ICBase-1 (74LS04).Connect Input-14 to Pin-1 (Input) of ICBase-1 (74LS04).Add IC 74LS21 into ICBase-3 (74LS21).Add IC 74LS04 into ICBase-1 (74LS04).