Stiebel Eltron SOM 7 Plus (RESOL DeltaSol BS Plus) differential temperature control with digital temperature display, programmable functions for solar domestic hot water systems and 10 selectable system layouts. 100-240 Volt operation. Control requires minimum of 2 sensors (4 are included) and will accept up to 4 sensors. 2 semiconductor outputs for pumps or valves and 1 output for VBUS data transfer.