A control word generator comprised of circuitry to generate a control word to control an attenuator. The method utilizes GATE message, report message format, and different data types of a multipoint control protocol to order various queues to make the queues have priority and transmit them sequentially in transmission. The cartridge is therefore installed and removed without binding since the user’s hand is centered as a result of the placement of the user’s hand in said handle. A position where at least one of the operation-related information and the measurement information is displayed is controlled according to the first display video signal or the second display video signal displayed by the display portion.