Federal Signal Modulator 8032B Voice and 2X Hi Lo | Cannon Falls MN 

Eden Prairie has a modulator that does alert and attack

bad video*

The 9th cell doesnt have anything in it iirc

The bottom cell doesn't have anything, it's empty. Reason being, every cell has speakers outputting the sound through the bottom of each cell above it, so the 8 cells are outputting the sound under them while the bottom cell doesn't have anything because the sound would be going down to the ground. This simply means hat since the sound is being ouput from the bottom of each cell, the sound is going down and outside of the openings.