Static transmitter stations are used to determine the position of a mobile receiver unit. Accordingly, the communication system can carry out efficient TCP congestion control by reducing a load of the TCP congestion control of the transmitters and receivers. Each of the linkages includes an upper link, a lower link, a front caster rod, a bottom link, and a rear link. The blower moves air into contact with radiation from the ultraviolet lamp. The erasing section uses the access port different from the access port of the reading section, to erase data that is stored in the flash memory and has been transferred by the reading section.