Epson BrightLink 421i Guide D'installation page 13

If you want to output audio from the external speakers (or use the microphone) when the projector is turned
off, you need to adjust the Standby Setup settings in the projector's Extended menu. In Standby mode, you
can output only Computer1 or Computer2 audio or composite audio (red and white RCA connectors).
HDMI connection
(video & audio)
RCA audio
connections
External speaker connection
Computer1 audio Computer2 audio
connection connection
Microphone connection
13
Ethernet connection
(video & audio)