Abstract: A refrigerator unit is configured for a container in which it is possible to know the quantity of air that is ventilated. The refrigerator unit is equipped with a ventilation mechanism, an opening degree detecting mechanism, and a recording unit. The ventilation mechanism ventilates the air inside the container. The opening degree detecting mechanism acquires ventilation data related to the quantity of air ventilated by the ventilation mechanism. The recording unit records the ventilation data acquired by the opening degree detecting mechanism.

Abstract: This invention relates to a rotational speed control system including a plurality of motor drivers for driving motors, and the object thereof is to drive a plurality of motors at the same rotational speed without depending on the number of motor drivers and without depending on the characteristics of each motor driver. A remote controller 31 and a motor driver 202 are connected to a motor driver 201. The motor drivers 201 and 202 control motors M11 and M12 at a prescribed rotational speed, respectively. A rotational speed instructing signal 91 indicative of the rotational speed is supplied from the remote controller 31 to the motor driver 201, and further supplied from the motor driver 201 to the motor driver 202. Because the rotational speed instructing signal 91 indicates a rotational speed which is transmitted in a digital value between the motor drivers 201 and 202, both of the motors M11 and M12 are driven at the rotational speed indicated by the rotational speed instructing signal 91.