From the manual @ http://www.hanvon.com/en/downloads/ebook/Manual/N520_English%20Manual_20090922.pdf Sleep: Select “Yes”, the system will sleep after 3 seconds if there isn’t any operation on the device, the LED indicator will turn off; select “No”, the system won’t sleep, and the LED indicator will always light. The system won’t sleep in this option: “Music”. Sleep Delay: There are three levels can be selected: short, middle, long. Select “short”, the system will get into sleeping mode quickly; select “long”, the system will get into sleeping mode slowly.