Integrated Circuits Used 74LS139 Procedure Add IC 74LS139 into ICBase-1 (74LS139).Connect Pin-1 (Input) of ICBase-1 (74LS139) to Input-14.Connect Pin-2 (Input) of ICBase-1 (74LS139) to Input-13.Connect Pin-3 (Input) of ICBase-1 (74LS139) to Input-12.