The aim of the invention is to optimize the running smoothness of an internal combustion engine. The transmission system may transmit 2-bit data for each transmission line set and each transmission line set may include first, second andor third transmission lines arranged in order. a digital wireless communications system and in particular to a method of and apparatus for mapping and demapping CDMA signals. If the mail placed on the mail platform is incoming mail, the platform is rotated to transfer the incoming mail to the underlying secure compartment, as well as to close the mail deposit opening. Then, an aqueous solution that contains a surfactant is added to this WO-emulsion, and the solvent is removed.