For now, "220V Cooling Fan" self-monitoring methods, respectively, and the speed sensor alarms both types, use alarm sensor gives an alarm signal DC fan speed falls below a certain threshold value, and the speed signal output can achieve real-time monitoring "220V Cooling Fan" speed. DC fan speed signal is generally output from the three-wire plug, three leads, yellow and black, respectively + 12V power and ground, another color of the line is the line speed signal output. It should be noted that some three-lead "220V Cooling Fan" of a third lead is not speed signal output line, but line speed control signal input speed control signal by which the DC fan motor.