Hi Sabre-RCU

If you have all your gear doors linked together through one valve (either servo operated or electronic) use D1. If you want your mains to close and your nose door to stay open plug your main valve to D1 and the nose valve to D2 and set the dial to MODE 3.

D1, D2 and D3 are for the door valves and MODE 1, 2 or 3 is how you want the sequencer to act. If you want to know what each Mode does let me know.

Good luck