Your favorite D/A converter may not be the latest but you like its sound, appearance and features. So you don't want to buy another expensive DAC just to connect a computer.
This is where these interfaces come in. The INT202 / INT203 allow any DAC to be connected to a FireWire or Thunderbolt ported computer. This is done, optimally, by slaving to the computer's internally generated clock with absolute bit transparency.
The INT203 is for bidirectional interfacing between AES/EBU and Firewire and also includes an infrared remote control for volume and absolute polarity. The bit transparency of the player software on the computer can be checked. The INT203 can serve as an input to the computer, e.g. to connect an A/D Converter for transferring vinyl records.