Asus Crosshair V Formula/ThunderBolt - Manual (Page 53)

6.. Thermal.sensor.cable.connectors.(2-pin.OPT_TEMP1/2/3)
These connectors are for temperature monitoring. Connect the thermal
sensor cables to these connectors and place the other ends to the devices
which you want to monitor temperature. The optional fan1/2/3 can work with
the temperature sensors for a better cooling effect.
Enable OPT.FAN1/2/3.overheat.protection in BIOS if you connect thermal
sensor cables to these connectors.
7.. Digital.audio.connector.(4-1.pin.SPDIF_OUT)
This connector is for an additional Sony/Philips Digital Interface (S/PDIF)
port(s). Connect the S/PDIF Out module cable to this connector, then install
the module to a slot opening at the back of the system chassis.
The S/PDIF module and the thermal sensor cable are purchased separately.
ROG Crosshair V Formula 2-23