An improved Nyquist filter can be used as a matched filter in a digital communications system. The control apparatus corrects during the start-up control current commands so that the AC voltage amplitude of the voltage commands will be a constant value not more than the maximum output voltage of a power converter. The mobile device’s display displays an image captured using the mobile device’s camera. The rearward discharge holes face proximally toward the applicator body, and the forward discharge holes face distally and outwardly from the head at an angle. The image server manages medical images together with information on the medical images based on the order information as additional information.