A radio communications system that eliminates limitation on usage forms of radio communication and enables users to implement radio communication easily. The cavitation reactor may be formed of a variety of fabrication techniques, include techniques used to form semiconductor devices. Thereby, a semiconductor memory device having a small chip size can be achieved. Based on PWM signals and by use of adequate switching logics for controlling multiple semiconductor switches, sophisticated control including zero-current switching and penetrating current prevention can be effected. The first, second, third and fourth guide members are located such that when a carriage moves rightward, the second contact surface and the fourth contact surface contact each other and after this, the first contact surface and the third contact surface contact each other. A mask pattern portion for exposing a predetermined pattern by an exposure beam is inspected by disposing a plurality of dummy inspection patterns having the same pattern as at least a part of the mask pattern portion, inside andor outside an area of the mask pattern portion and comparing at least the portion of the mask pattern portion with the dummy inspection pattern portion or portions.