The Little Giant 950887 DA-60-12WA-1 is a 60-watt 12-volt transformer with a built-in photocell.  It has a 3-foot cord and a 3-prong grounded plug. The transformer is cUL listed and should be used outside of a pond. It has a programmable timer that can be set to shut off in 4, 6, or 8 hours. This can help save electricity and extend the life of the bulb.The transformer has a durable epoxy-sealed housing and includes a quick-connect fitting for easy installation. It comes with a 1-year limited warranty.It works by checking the sunlight. If it's light outside, the lights are off. When it gets dark, the photocell triggers the transformer to turn on the lights. The lights stay on until the sun comes up.