Diplexing is employed in systems having multiple differential conductor pairs. A first differential coupling differentially couples a first signal onto a first pair of conductors; a second differential coupling which differentially couples a second signal onto a second pair of conductors; a first common mode coupling selectably common mode couples a third signal onto the first pair of conductors; a second common mode coupling selectably common mode couples a fourth signal onto the second pair of conductors; and a switch is operational to select the first common mode coupling or the second common mode coupling based upon a triggering event.