A mobile station and unattached work area is used with an electronic pen, which includes a transmitter, such as an acoustic transmitter. The organic EL portion includes a first electrode, an organic layer, and a second electrode sequentially stacked, and a nano-porous layer and a highly refractive layer are interposed between the rear substrate and the first electrode. The sensor output signal may be indicative of the patient’s heartbeat, or other physiological event.