There is provided a DC-DC converter circuit with which conduction loss between switching elements is lower than in the conventional art, which affords an increase in power conversion efficiency. The system includes a wavelength demultiplexer that optically receives an OCDMA signal having a plurality of wavelengths of light. The measurements are then compared to the threshold to determine whether ringback is present. The LED is received in the cavity. The gateway may use an IBE decryption engine to decrypt the incoming message. Accordingly, the AV data and the control data can be transceived over the single channel in the HDMI.