ASRock B75 Pro3 manual Chassis Speaker Header Please connect the chassis

Though this motherboard provides 4-Pin CPU fan (Quiet Fan) support, the 3-Pin CPU fan still can work successfully even without the fan speed control function. If you plan to connect the 3-Pin CPU fan to the CPU fan connector on this motherboard, please connect it to Pin 1-3.Pin 1-3 Connected

3-Pin Fan Installation

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Chassis Speaker Header	Please connect the chassis
(4-pin SPEAKER 1)	speaker to this header.
(see p.13, No. 16)
Power LED Header	Please connect the chassis
(3-pin PLED1)	power LED to this header to
(see p.13, No. 22)	indicate system power status.
	The LED is on when the system
	is operating. The LED keeps
	blinking in S1/S3 state. The
	LED is off in S4 state or S5
	state (power off).
Chassis and Power Fan Connectors	Please connect the fan cables
(4-pin CHA_FAN1)	to the fan connectors and match
(see p.13, No. 37)	the black wire to the ground pin.
	CHA_FAN1 and CHA_FAN2
	supports Fan Control.
(3-pin CHA_FAN2)
(see p.13, No. 10)
(3-pin PWR_FAN1)
(see p.13, No. 36)
CPU Fan Connectors	Please connect the CPU fan
(4-pin CPU_FAN1)	cable to the connector and
(see p.13, No. 1)	match the black wire to the
	ground pin.