Both the WL500 and WL300 can be used to implement this application
In case you have available connection to the public water system, the automatics can be installed as a level indicator, to know the level of water in your tank.
WL-300
Place the floating and the contaniner together, one onto the other, placed to an aproximately height of middle of tank, and wire cables red and white to a low consume bulb lamp (prefereable neon). This lamp will turn on only when water level has reached below your setting (the floating and container, see figure 1 below) and will keep turn off while water level is over your setting.
Conections
diagram of a level indicator using WL-300
Special Feature
