So apparently many macbook pro models have a digital audio output hidden inside their 3.5mm headphone jacks. Example.
I thought this was physically activated by the mini TOSLINK plug, but recently I installed Linux Mint (native boot) on my MBP and that red light came on and stay on.
So I guess it can be controlled by software.
Anyone know how to activate it in macosx? The only reason I want to turn it on is I think it looks cool.