I need some basic electrical engineering type help in understanding how fan speeds are regulated. Most case fans these days come with motherboard headers or switches/sliders to control their speeds.

Deciding between PWM and DC case fans can be confusing, but it’s important for the optimal performance of your computer. In general, PWM fans are quieter, more controllable, and more durable than DC ...

Withclosed loop speed control, the fan controller ensures that the fan isrunning at the desired speed by measuring the actual speed and adjustingthe duty cycle accordingly. Here the host specifies the ...