This sets a hysteresis at which switchover to the next fan speed occurs. The hysteresis applies for all three
threshold values.
The setting 0 causes immediate switching without hysteresis.
The entered percentage value is directly added to or subtracted from the percentage value of Threshold
value speed x. The result is a new upper or lower threshold value.
Switch threshold top (switch on) = threshold value + hysteresis
Switch threshold bottom (switch off) = threshold value - hysteresis