SOYO 5EAS5 P55C - Manual (Page 21)

Hardware Setup
17
J23: Sleep Switch Connector Enable/Disable
Toggle this jumper to force the system into power saving (green) mode.
Any hardware IRQ signal will cause the system to wake up.
CN3: Universal Serial Bus Connectors
Attach a 9 pin USB cable to these connectors to connect external USB
devices to the mainboard.
J18: Speaker Connector
Attach the connector from the speaker in your case to this jumper.