InFocus Interactive White Board User Manual page 16

Connect to media display
Digital Optical Cable Output (SPDIF)
Use digital optical cable to support SPDIF
Because of different equipment and software, digital optical cable
(SPDIF) probably cannot output some signals.
Earphone Output
Connect 3.5mm audio cable between the earphone output terminal
of display and the input terminal of audio power amplifier or active
speaker.
16
Not using earphone, please pull out the plug.
After inserting earphone, the speakers of the display do not
have audio output.