"Micro Cooling Fan" tachometer 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 of a third wire DC fans are not speed signal output line, but the speed control signal line speed control signal input through which the "Micro Cooling Fan" motor. So far, the fan has their own way of monitoring alarm and the speed sensor are two types of alarm sensors can use the fan speed is lower than an alarm signal when a certain threshold, while the speed signal output fan speed can be realized in real time monitoring. "Micro Cooling Fan" speeding motor manufacturers preferred Xin Xin speed is your best choice.