Asus Z9PH-D16 - Manual (Page 48)

2-30 Chapter 2: Hardware information
7. ASMB6 header (ASMB6)
The ASMB6 connector on the motherboard supports an ASUS ® Server
Management Board 6 Series.
8. Thermal sensor cable connectors (3-pin TR1, TR2)
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.
Please go to BIOS setup to change the default setting of TR1/TR2 from
“disabled“ to “enabled“ before using the thermal sensor cable.