A surgical device adapter assembly comprising: a tubular housing having a proximal end portion configured to couple to a handle assembly, and a distal end portion configured to couple to a surgical end effector; an electrical connector disposed at the proximal end portion; an electrical contact assembly (80, 81) disposed at the distal end portion; and a wire harness disposed within the tubular housing and interconnecting the electrical connector and the electrical contact assembly, wherein the wiring harness is a flexible cable having a first flexible dielectric substrate, one or more conductive layers disposed on the first flexible dielectric substrate, and a second flexible dielectric substrate, wherein the one or more conductive layers are enclosed between the first flexible dielectric substrate and the second flexible dielectric substrate; wherein the adapter assembly further includes a switch actuated in response to the surgical end effector being coupled to the adapter assembly; wherein the flexible cable is coupled to the switch and includes a flexible finger (84, 86) coupled to the electrical contact assembly; and wherein the surgical device adapter assembly further comprises a rotatable lock member at the distal end of the adapter assembly configured to engage the surgical end effector. a tubular housing having a proximal end portion configured to couple to a handle assembly, and a distal end portion configured to couple to a surgical end effector; an electrical connector disposed at the proximal end portion; an electrical contact assembly (80, 81) disposed at the distal end portion; and a wire harness disposed within the tubular housing and interconnecting the electrical connector and the electrical contact assembly, wherein the wiring harness is a flexible cable having a first flexible dielectric substrate, one or more conductive layers disposed on the first flexible dielectric substrate, and a second flexible dielectric substrate, wherein the one or more conductive layers are enclosed between the first flexible dielectric substrate and the second flexible dielectric substrate; an electrical connector disposed at the proximal end portion; an electrical contact assembly (80, 81) disposed at the distal end portion; and a wire harness disposed within the tubular housing and interconnecting the electrical connector and the electrical contact assembly, wherein the wiring harness is a flexible cable having a first flexible dielectric substrate, one or more conductive layers disposed on the first flexible dielectric substrate, and a second flexible dielectric substrate, wherein the one or more conductive layers are enclosed between the first flexible dielectric substrate and the second flexible dielectric substrate; wherein the adapter assembly further includes a switch actuated in response to the surgical end effector being coupled to the adapter assembly; wherein the flexible cable is coupled to the switch and includes a flexible finger (84, 86) coupled to the electrical contact assembly; and wherein the surgical device adapter assembly further comprises a rotatable lock member at the distal end of the adapter assembly configured to engage the surgical end effector.