The Johnson AS888 Automatic Bilge Pump Switch provides a full automatic bilge pumping operation when connected to your bilge pump. The AS888 automatic switch has a time-proven micro switch without mercury. When water exceeds the acceptable level, the pump is turned on by a rolling steel ball, which changes the pressure on the micro switch. The AS888 attaches to any SPX Johnson Pump Marine bilge pump through the clip on ?T-slot? and can be used with 6, 12, 24 or 32 V systems. Use the Johnson AS888 Automatic Bilge Pump Switch for a better and safer life afloat!