The logic for this system is fiendishly simple, and involves no transistors. Nonetheless,
it was easier to buy the Levelite controller than run around getting all the relays and
associated parts. I don't live near a Fry's anymore.
There are two main advantages to this design. First, the pump doesn't start and stop pumping small amounts of water, but waits untill the tank is full. Second, the sensors operate at 12 volts DC, which is a lot safer and easier than running 120 volt outside and immersing it in water.
Front panel includes a power switch, mode setting, manual cycle start and operating instructions.