Station programming screen A.Look at an extension number for the vx2 and extension ports and check the keys as to how they are programmed.Adirect trunk key is a key for a specific line.Like if you had 3 lines then you would have keys for lines 1,2 and 3 on the sets ie key codes 001,002,003 .Trunk keys are a key(s) that grab you an available line when dialling out and where incoming calls would appear.ie key code 300