Epson EMP-5500 Owner's Manual page 92

Serial. A type of communication interface that transmits data
over a single wire.
Sleep mode. The power cable is connected but the projector
is switched off. In this mode the power LED lights up orange.
If the projector is not used for 30 minutes the lamp switches
itself off and after 30 seconds the projector goes into sleep
mode.
70 Glossary