Here's the schematic (from Audiotec-Fischer) useful for makin your own remote controller compatible with the DSP's from Helix (P-DSP and C-DSP) and Brax (NOX4 amplifier built-in DSP).

Apparently this thing is A MUST if you have only one sound source, you connect it thru the optical fiber and you would like to control the volume level of your system

You will need a 10k Ohm linear potentiometer (or 2 if you'd like to have the sub control too) and a 12pin male "Micro Match" type connector (1.27 mm pin threshold)

Most potentiometers will have 3 connectros they're A C B no matter from which side you look. (but remember they will work "from the left to the right" for the side you looked from ) so... you connect:
A) +3.3V
C) control signal (main remote / sub remote)
B) ground (masse)

Of course you can have the + and - "bridged" till your potentiometers - so for two pots you'll need 4 Wire cable.

Helix DSP Remote Controller Schematic.jpg

DSP Level Regler.pdf

If you'd have any problems with locating the pin numbers - here's explanation.

Pinning MicroMatch Control Input.pdf

I still don't know what the "Switch" connectors are for. Will post an update when find out (I believe they are for swithing between 2 saved configs but I'm not sure yet)