PWM based control
While most fan controllers are voltage based, the NA-FC1 uses the more sophisticated Pulse Width Modulation (PWM) technique that allows for more efficient control and lower minimum speeds, regardless of the fan’s starting voltage.
Manual control mode
If the NA-FC1 doesn’t receive an input PWM signal from the motherboard, it works as a simple and efficient manual controller that allows the duty cycle to be set from 0 to 100%. This makes it ideal for manually slowing down high-speed PWM fans such as Noctua’s industrialPPC series in order to achieve consistently quiet operation.
Customising motherboard fan control
Many motherboards provide insufficient options to customise automatic fan control or simply don’t go below certain duty cycles and speed levels. Using the NA-FC1, you can lower the motherboard’s PWM control curve in order to achieve truly silent operation, even with high-speed PWM fans such as Noctua’s industrialPPC series.
“No stop” mode
If the small push button is pressed and the green status LED is on, the NA-FC1 operates in “no stop” mode, which means that it will not allow the fan to fall below 300rpm, regardless of the speed setting and the input PWM duty cycle from the motherboard, thus avoiding BIOS fan errors.*
3-way splitter cable
The supplied 3-way splitter cable allows the connection of up to three 4-pin PWM fans in order to control them simultaneously. Even more fans can be controlled at once when using additional NA-YC1 splitter cables that are supplied with many Noctua fans and available as an optional accessory kit (NA-SYC1).
Power supply adaptor
As powering multiple higher wattage fans from a single motherboard fan header may damage the motherboard, the NA-FC1 includes an NA-AC4 adaptor that powers the device directly from the power supply unit while simultaneously receiving PWM input from the motherboard and forwarding RPM information. This makes it ideal for controlling multiple high-speed fans such as Noctua’s 3000rpm industrialPPC models.
Source : Noctua NA-FC1 Fan Controller