A method and apparatus for mesh based protection of an optical network is described. By disposing at least one junction region of the Zener diode outside of the base region of the transistor, a tight and suitably high reverse breakdown voltage is achieved. , a hash code of the serial number is registered in the user information. A high potential bias voltage input terminal of each of remaining DACs except the uppermost DAC is cascade-connected to an output terminal of an upper DAC next to each of the remaining DACs. The surface of the photoconductor has such roughness as to provide I of at least 3. The system includes a large storage compartment to allow storage of large items such as all terrain vehicles, motorcycles, bicycles and other large items even when in the compact transporting configuration.