Can someone help me with switch in headlamp bucket

[amanda11270]

Im not sure I understand the switch in the headlamp bucket, I thought I remembered reading the switch should only be in one position, but im not sure which, as mine is not marked. I can say that in one position with the bike's key turned on to either key position, the tailight is not on, in the other headlamp bucket switch position the tailight comes on in both key positions. What is this switch's purpose, and which position should I have it in?

The reason im concerned is I got my new headlamp and it was about $60 and dont want to burn it out. I have not wired it in yet because of this switch, dont want to have it in the wrong position.

[amanda11270]

I think I found a post where Roger answered this question for me already, except I misunderstood and thought I wanted the DC position, when I want the AC position where the headlamp runs only off the magneto and not the battery.