A two-channel directional antenna for use in a radar level gauge. The apparatus includes an image-forming element which forms an image, an ocular unit which causes light from the image-forming element to form an exit pupil, and an optical element which reflects the light from the image-forming element toward the ocular unit. In some embodiments, collisions during the exchange may be reduced by having different network devices use different sub-channels or different time slots. The microprocessor monitors the output voltage of the first and second battery groups. Users may select patients and dispense medications by reading the indicia from the reports using the reading device. Each of the at least one hydraulic-pressure control valve group includes at least one ONOFF control valve and at least one linear control valve that are disposed in parallel with each other.