Abstract: The apparatus includes a high frequency, high voltage generator, a therapeutic instrument for applying an electric current to a patient, a compound electrical power and control cable connected between the generator and the instrument, and a switch for selectively connecting at least one signal current conductor in the cable to a therapeutic current conductor in the cable to complete a circuit through an activating device for controlling the action of the generator. The cable includes a multiple strand bare therapeutic current conductor wire and preferably two single strand wires with film coatings of low voltage insulation, all of the wires being enclosed in a protective sheath of high voltage insulation. A high voltage is impressed on all of the wires but the voltage differential is very small so that the bare conductor is adequately insulated from the others by the film coatings, with a resulting savings in weight and cost of wire and insulation and improved flexibility.