"Waterproof Cooling Fan" Voltage Voltage - [V] is calculated in units of volts, standard computer fan voltage DC12V, factory specifications and may depend on the needs of the home with a muted down to 7V or 5V. Fan speed will slow down, bearing sound, wind noise and other noise decreases, in exchange for air volume and pressure will diminish.
"Waterproof Cooling Fan" PWM electronic pulse frequency modulation - Pulse Width Modulation [full name], mostly used in CPU (with a small 4-pin socket) on. In a nutshell is the temperature sensing element (Sensor IC) computer motherboard temperature data transfer to the Main Board of the Signal Generator (signal conversion) electronic components, and then generates a pulse signal with speed control IC electronic components on the circuit board, according to "Waterproof Cooling Fan"factory default program options through conversion (trimming fan voltage) to control the fan RPM, achieving low temperature and high temperature high to low turn temperature effects.