MSI 815 PRO Manual page 29

The JMDM1 connector is for use with Modem add-on card that supports
the Modem Wake Up function. To use this function, you need to set the
"Power On by Ring" to enable at the BIOS Power Management Setup.
Note: Modem wake-up signal is active "low".
Note: To be able to use this function, you need a power supply that
provide enough power for this feature. (Power supply with 750mA
5V Stand-by)
PIN
1
2
3
4
5
2-25
JMDM1
SIGNAL
NC
GND
MDM_WAKEUP
NC
5VSB
5
1