Pro Tools 4.3.1 and later uses the GPI outputs as follows:GPI Output 0 (relay): PlayGPI Output 1 (relay): Record ReadyGPI Output 2 (relay): Fader Start #1GPI Output 3 (relay): Fader Start #2GPI Output 4 (TTL): StopGPI Output 5 (TTL): RecordingIn addition, Pro Tools uses some of the above for the following modes:- Transport Cueing, Shuttling, or Jogging: GPI 2 and GPI 3 simultaneously ON- Transport Fast Forward: GPI 2 ON- Transport Rewind: GPI 3 ON- Transport Cued: GPI 4 ON- Transport Paused: GPI 0 and GPI 4 simultaneously ON