Saab: Avoiding Battery discharge

My fog lights operate only when the light switch is in the head lights
on position and the fog light dash button depressed.When this is on, I
have no headlights

What is irksome is that this configuration does not allow the lights
to be tuned off (as would the head lights)and I have inadvertantly run
down the battery as a result.

Is this normal? Can it be easily altered so that the fogs too would
not operate with the key off?

Malcolm