Package included：1 x 12V40A 480W Regulated Switching Power Supply (power cord is not included). Be sure to confirm the input and output voltage first: 1. You can choose the proper input voltage (110V/220V) by a black switch to avoid damaging. Left is: AC 110V, Right is AC 220V. Please set the switch to 110V for USA/CA. 2. The 12V 40A output voltage can be regulated by ±15%, which greatly expand its application range. There is a yellow botton on the right corner. Turn the yellow button clockwise, the output voltage could be fine tuning. 3. The max use of power should be no more than 80% of the full loads, otherwise,the power supply's spanlife will be shortened. We recommend you to use this 12V 40A 480W power supply to power devices less than 32A 384W. 4. This Unit "DOES NOT" comes with installation instruction, wiring cable, on/off switch, or screws. Professional installation of qualified electrician is highly recommended. 5. High Voltage inside, do not remove the cover. Dust the switcher out every 2 or 3 months if necessary. Over Voltage Protection, Overload Protection，Over Current Protection, Over Temperature Protection， Short Circuit Protection Why does the LED power supply stop working？ Maybe the overcurrent protective switch (in the power supply) disconnect. Please unplug your AC cable, it's important! Then wait about 10 minutes. It will be auto recovered. Then reconnected it, it will work well.