I need to sense a multiple switch closures externally to the circuit that is in operation.
One lead is a +5VDC strobe and the other lead is the return, both originating on a CPU. The switch is part of a large switch matrix where the strobes are columns and the returns are rows.
Naturally the sense circuit must not result in a false switch closure nor cause the inability of
the matrix circuit to detect a switch closure.
For some reason I am in a fog on the solution to this problem.