Sony Philips Digital Interface. It's a two channel digital I/O.

Those 2 little RCA connectors would allow you to use an external analog to digital converter with a similar SPDIF output. With the M-Box 2, this would give you the ability to input 4 channels to 4 separate software tracks. I've used those in exactly that manner on mine. Instead of a separate analog to digital converter, I just grabbed one of my old DAT machines whose heads are trashed. So it is getting used simply as an analog in to digital out device. So if you can find yourself a broken used Panasonic SV3500/3700 or SVDA10, or the TASCAM DA20/30, you'll be able to record with 4 inputs.

This is not true of all equipment however it is applicable to your M-Box 2. But many pieces of equipment have those same digital inputs and outputs as they were in early standard digital transfer method. Each SPDIF signal is a stereo pair and so carries 2 channels on a single connector. So your M-Box can accommodate a single digital input and provide a single digital output of stereo.

Got it? Get it.
Ms. Remy Ann David

can you use a 75 ohm video cable to double as an spdif cable?

Well, it's a piece of coax which should do the job. Might have a little trouble trying to solder to RCA connectors however? If you're not going to run your line too long, almost any kind of hi-fi RCA audio cable will do. If you need to run it an appreciable distance, more than 10 feet (3.1 meters), you won't want to be using SPDIF but AES 3? Which is balanced, utilizing 110 ohm microphone cable. But the gizmo has to have that connection already in place. I don't know of any converters to do that? I'm sure a few other folks will chime in here?

Sony Philips digital Incredible Freakout
Ms. Remy Ann David