Explanation of Access Controller Pro 2 connections needed

Hi, Can some explain the individual connections of the terminal block and which ones I should be using? I need to connect to my gate opener control board which has: COM - common OPEN - to open gate If these are bridged, then the gate opens. I was expecting the ACP2 to have 2 relay connections COM - common NO - normally open Which would connect directly to my control board COM to COM NO to OPEN The ACP2 terminal block has 8 connections: Ext: +5v Port A: D1 D0 GND Port B: REL1 REL2 Power: PS1 PS2 Which ones should I connect up to where? Thanks in advance Dave