The SweepZone technology uses "Smart Circuit", a custom-engineered electronic component that creates Constant Power Output (CPO) for consistent, uniform cleaning. This technology incorporates Pulse Width Modulation (PWM), which enables the SweepZone Ag to sense cleaning loads, solution level and voltage fluctuations. It automatically adjusts to different conditions to create uniform cleaning power-eliminating hot spots and weak areas. SweepZone Ag systems: Use a special cleaning wave of +/- 2 KHz energy that sweeps back and forth through the tank. Provides complete cavitation. Provides aggressive cleaning action. Are all backed by our unprecedented 21ò2 year warranty. Timer and drain standard on all units. This recessed unit comes with standard lid.