how does comline filter work?

[uhuru]

I just got the tunze reefpack 500 and haven't set it up yet, but by looking at it I cannot figure out how the comline filter part of it works. The pump pulls water from the "bell shaped" filter, but how does water from the tank get INTO the bell shaped filter? Here is a pic of the part.... how does water get into here?

 

[rvitko]

There is a circular slot on the bottom where the water comes in and there is a hole with a strainer in the middle where the water is sucked through by the pump.