A bone access instrument comprising a shaft having a first shaft portion and a second shaft portion. The air dryer cartridge comprises a supporting element. Mutually different modes can be obtained when discharge is produced independently in the discharge sections. An injection circuit mixes code signals into video signals. The method comprising the steps of forming a gap in the conductive film located between the electrodes, and applying a voltage between the electrodes in an atmosphere that has an aromatic compound with a polarity or a polar group and in which the partial pressure ratio of water to the aromatic compound is 100 or less.