Turn off the DDX3216 and the 003 Rack. This is a general safety precaution that should usually be taken when connecting wires between studio devices.
Connect one end of the first standard 5-pin MIDI cable to the "MIDI Out" port in the back panel of the DDX3216.
Connect the other end of the first MIDI cable to the "MIDI In" port at the back of the 003 Rack.
Connect one end of the second MIDI cable to the "MIDI In" port at the back of the DDX3216.
Connect the other end of the second MIDI cable to the "MIDI Out" port at the back of the 003 Rack.
Turn on the DDX3216 and the 003 Rack.
Open Pro Tools. You will now be able to control on-screen faders and knobs in Pro Tools using the DDX3216.
Make sure that the DDX3216 and the 003 Rack are turned off.
Plug the ADT1616 ADAT interface into one of the "option slots" at the back of the DDX3216. The ADT1616 is sold separately and is required in this case for its optical in/out port. The DDX3216 does not have a built-in optical port.
Connect one end of the optical cable to the port marked "Optical" at the back of the 003 Rack.
Connect the other end of the optical cable to the optical port labelled "Out 1-8" on the ADT1616 module.
Turn on the DDX3216 and the 003 Rack.
Open Pro Tools. You will now be able to run an audio signal directly from the DDX3216 through the 003 Rack into Pro Tools with ADAT-quality sound and minimal latency.