The Viqua 650709-004 is replacement power supply kit (also called a controller) that is used to replace the power supply of a Viqua system. The 650709-004 is the newest version of the company's line of G, H, J, and K/Plus controllers and is used for the Viqua system. The Viqua 650709-004 plugs into a wall outlet and acts as a transformer - taking the native voltage and amperage and converting it to the proper voltage and amperage for the UV lamp. It also provides valuable information to the UV system operator in the way of a digital readout, making it easy for you to determine UV purification levels and the need to replace the controller again.