SDP-3500 DC Variable Frequency Pump Description: The low voltage 24v dc frequency conversion technology, saveenergy and more secure. 10 grades speed change, flow rate adjustable. New wave function, let you have more characteristic of water cycle. Both fresh water and marine water, use ceramic shaft, long service time. Use sine wave technique, low noise. 1C electronic detection, automatic anhydrous protection and locked-rotor protection, abnormal error reporting. The new design of the bottom filter cover is more conducive toremoving the waste from the bottom of the filter tank.