Suppose a system S1 with 4 outputs and a system S2 with 3 inputs. Each input and output of both systems is 1-bit. Design an interface circuit so that each input of S2 can accept information selectively from whichever output of S1, independently from the other inputs of S2.

A) Which basic circuit is the most appropriate to use in the design of such an interface circuit ?

B) Design the interface circuit, using as many copies of the circuit selected in subquestion A, as necessary.

(My guess on subquestion A is the multiplexer. Not sure though.)