MBox 3 (not mini or Pro) Channels 3 and 4.

[scottie_uk]

So I have an MBox 3 (not mini or pro). On the driver control panel, what are hardware inputs 3 and 4 used for on both the ditial and analog hardware inputs? The manual shows them, but a search for "channel 3" or channel 4" or "Input 3" / "Input 4" on the manuals PDF returns nothing but a small mention that tells me little and maybe is incorrect. I read the whole chapter on the driver; it does say "Hardware Inputs 1–2 are the analog inputs, and Hardware Inputs 3–4 are the S/PDIF input L/R.". However, I'm not sure this is true as the S/PDIF are also on 1 and 2 but on the different tab only for digital inputs.

So what are inputs 3 and 4 on the digital and analog sides and how to I activate and use them?