A cannula for use with a matable supply electrode assembly having a coupling assembly, wherein a supply electrode is supported by and projects outward from the coupling assembly, the coupling assembly being connected to a cable that connects the supply electrode to a control console that generates electrical energy of a controlled radio frequency, said cannula comprising: an electrically conductive outer tube with opposed proximal and distal ends and a through-bore; an electrically insulated hub attached to the proximal end of the outer tube, the hub dimensioned to releasably engage with the coupling assembly; an electrically conductive inner tube disposed concentrically to and radially inward from the outer tube, defining an axially extending through-bore for receipt of the supply electrode and projecting axially forward to a distal end, wherein the distal end of the outer tube is spaced proximally rearward of the distal end of the inner tube; an electrical insulating inner sleeve orientated concentrically to and radially outward from the inner tube and projecting axially from the hub, wherein the inner insulating sleeve does not extend axially forward as much as the inner tube, so that a portion of the inner tube at the most distal end of the inner tube is exposed to the environment as a first active contact of the cannula; an electrical insulating outer sleeve orientated concentrically to and radially outward from the outer tube and projecting axially from the hub, wherein the outer sleeve does not extend axially forward as much as the outer tube, so that a section of the outer tube at its distal end is exposed as a second active contact; and an electrical terminal seated in the hub for establishing a conductive path from the outer tube to a complimentary terminal of the coupling assembly, so that the second active contact functions as a return electrode for a signal generated by the control console; characterized in that: the hub comprises an alcove that opens radially outward and axially rearward, wherein a tab projects forward from a cartridge of the coupling assembly and into the alcove, when connecting the supply electrode assembly; and the electrical terminal is seated in said alcove in the hub so that, when the tab projects into the alcove, the coupling assembly complementary terminal, which is mounted to the coupling assembly cartridge tab, contacts the electrical terminal; wherein, when received in the through-bore of the inner tube of the cannula, the supply electrode serves as the component that completes the conductive path from control console through a plug and the cable, to the first active contact of the cannula. an electrically conductive outer tube with opposed proximal and distal ends and a through-bore; an electrically insulated hub attached to the proximal end of the outer tube, the hub dimensioned to releasably engage with the coupling assembly; an electrically conductive inner tube disposed concentrically to and radially inward from the outer tube, defining an axially extending through-bore for receipt of the supply electrode and projecting axially forward to a distal end, wherein the distal end of the outer tube is spaced proximally rearward of the distal end of the inner tube; an electrical insulating inner sleeve orientated concentrically to and radially outward from the inner tube and projecting axially from the hub, wherein the inner insulating sleeve does not extend axially forward as much as the inner tube, so that a portion of the inner tube at the most distal end of the inner tube is exposed to the environment as a first active contact of the cannula; an electrical insulating outer sleeve orientated concentrically to and radially outward from the outer tube and projecting axially from the hub, wherein the outer sleeve does not extend axially forward as much as the outer tube, so that a section of the outer tube at its distal end is exposed as a second active contact; and an electrical terminal seated in the hub for establishing a conductive path from the outer tube to a complimentary terminal of the coupling assembly, so that the second active contact functions as a return electrode for a signal generated by the control console; characterized in that: the hub comprises an alcove that opens radially outward and axially rearward, wherein a tab projects forward from a cartridge of the coupling assembly and into the alcove, when connecting the supply electrode assembly; and the electrical terminal is seated in said alcove in the hub so that, when the tab projects into the alcove, the coupling assembly complementary terminal, which is mounted to the coupling assembly cartridge tab, contacts the electrical terminal; wherein, when received in the through-bore of the inner tube of the cannula, the supply electrode serves as the component that completes the conductive path from control console through a plug and the cable, to the first active contact of the cannula. the hub comprises an alcove that opens radially outward and axially rearward, wherein a tab projects forward from a cartridge of the coupling assembly and into the alcove, when connecting the supply electrode assembly; and the electrical terminal is seated in said alcove in the hub so that, when the tab projects into the alcove, the coupling assembly complementary terminal, which is mounted to the coupling assembly cartridge tab, contacts the electrical terminal; wherein, when received in the through-bore of the inner tube of the cannula, the supply electrode serves as the component that completes the conductive path from control console through a plug and the cable, to the first active contact of the cannula.