FS is an Oceanus Systems Auto Top-off unit - Atlas.

This unit is great - it has 3 float sensors & a dual CGFI outlet:
1. Water low - openes solenois to fill sump
2. HIGH WATER ALERT (sump) - If water level reaches & trips this sensor, Visual & Audible alert activates & Solenoid will close if not already. (CGFI will stay powered up - return pump will continue to run)
3. LOW WATER ALERT (sump) - If water falls below this low level sensor, Visual (red Light) & Audible alert activates & it will kill power to the CGFI (return pump) - this alert also opens the solenoid to fill - in case first sensor didn't open it)
4. HIGH WATER ALERT (display tank) - In case one of your drain pipes clogs - This sensor is for the display - in case water level reaches & trips this sensor, Visual & Audible alert activates, and power to CGFI will be cut - return pump shut down to prevent a dry sump, and wet floor.

#1 & #2 are 2 differnt float switches - but both are on 1 assembly.

I purchased this unit on August 1, 2006 - but did not use it until ~ November when i got the 150g up & running.

Pictures can be found at the below link (in my gallery)
http://swfmas.com/v/users/wiszmaster/ato

Price $175 obo - I paid over $200 for it less than a year ago, and the unit is in great condition.