Epson 500 Series - Manual (Page 44)

Using the Suspend/Resume Switch
The suspend/resume switch provides an efficient way to save
battery power. This switch is located on the top left side of the
computer.
Slide the suspend/resume switch to the right to temporarily stop
system activity when you do not need to use your computer for
short periods of timt. The screen goes dark and the computer
suspends power to its components and devices; it continues to
supply power to the RAM. (If you are not going to use the
computer for a longer time--20 minutes or more, for
example—turn it off.)
To resume activity, slide the switch to the left or press the Shift
key. The computer resumes normal operation at the point at which
you suspended it.
Powering the Computer 3-7