cant remember what they are called but them big spinning speakers were the ones to stand next to......................at least two hours for ears to go back to normal
Delks have a sensitivity dial on them. Like Frothey says, if you set them too sensitive they will be bleeping all the time. You adjust them to the conditions so that they wont go off with each gust of wind.
Some of the fox alarms have sensitivity control on them,only top end ones.
After looking closely at delcs and fox there seems little difference between the two.
Not having tried either of them yet I'm still on the fence.