A rotary terminal mechanism in which a first electroconductive ring is inserted, under a slightly collapsed state, between the circular internal peripheral surface of a first outside electrode and the circular external peripheral surface of a first inside electrode that are arranged concentrically. The method comprises the step of determining whether a voice function request signal is input or not, switching a vocoder into a digital mode for operating the voice function, and operating the voice function in digital mode. An operating tube enters a brain according to the brain surgical route data.