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Design (and possibly provide prototype) of a circuit to detect low water level and activate a fill valve. Power input is 120v 60Hz AC, output to valve is 24VAC. Circuit would use a sensor that detects continuity between two contacts, using very low voltage/current so that it is intrinsically safe against electrocuting swimmers. Circuit would include an overfill lockout that would disable the fill function for 24 hours if low water level is sensed for more than 20 minutes. Circuit should include LEDs to inform user of functions (power, low water, fill valve, lock-out).