"220V AC Cooling Fan" is energized If the fan rotation is stopped, it will output ALARM. When the fan slows down to a certain speed, which began output ALARM. Output using non-contact type. When the fan slows down to a certain speed, which began output ALARM. Using contact-type output. Fan per revolution that is double the output pulse signal. Because the main controller and other receiving pulse output can monitor the speed, and therefore also for those who want the freedom to use when setting ALARM output speed.