A surface active agent composition is prepared including: a polymerizable monomer surface active agent and a polymerizable dimer surface active agent represented by the following chemical formula. The compensation apparatus compares the resistance of a resistor in the circuit with the resistance of a reference resistor. Any payment due is paid according to a pre-established payment cycle. The gripper can move more quickly to the next object to be picked up. An expansion module bay including a module sleeve having an opening for receiving the expansion module is described. While being transmitted via the respective transmission lines, these message cells pass through a buffer memory individually allocated thereto.