A method is disclosed for determining whether to transmit from a first unit to a second unit, where the transmission is one of a first type and a second type. If the coupling coefficient between the two antennas 107 and 109 is k, then fs and fp are set so as to satisfy the inequality \u22121. Each of the first and third capacitor electrodes is electrically connected with the second pixel electrode. The numerical aperture NA of the lens in the arrangement direction in the lens array satisfies the formula NA>sin with respect to the maximum angle of view \u03b8max of the focusing unit. Thus, the PLC can receive data from the terminal device, or can transfer predetermined data to the terminal device through the inputoutput controller of the present invention. If the lost frame detector determines that the encoded frame is erased, a FEC module applies a frame concealment process to the signal.