Epson 73c - Manual (Page 20)

14 Setting Up the Projector
4. You can connect an external mouse to the USB Type A port or
use the port as a USB hub to connect an external USB device, if
you want.
If you don’t need to make any other connections, you can plug in
your projector and turn it on. See page 20 for instructions.
Amplifying Computer Audio
Your laptop probably has its own sound system; however, it may not
be adequate for your presentation. If you need more volume, you can
connect a computer audio cable to take advantage of the projector’s
built-in amplifier and speaker. You can obtain a computer audio cable
(3.5-mm stereo miniplug cable) from a computer or electronics dealer.
1. Connect one end of the audio cable to the Audio1 jack on the
projector.