Littelfuse Model ALT-230-S Alternating Duplex Pump Relay 195-250V 8-pin Plug-inLittelfuse ALT 230 S Alternating Duplex Pump Relay Product Description Model ALT 230 S alternating relays are used to alternate between two loads. The ALT is commonly used in duplex pumping applications to balance the runtime of both pumps. The Model ALT S is used in single high level float applications. When the float switch opens, the alternating relay changes state forcing the other pump to run the next time the float closes Littelfuse ALT 230 S