The Power Supply Input is For The Backlight for,And Adjustable Resistance for Adjust jump Performance: temperature 2%, humidity 70%, if there is no difference in the test results, it can run at normal temperature and humidity. note :The cable need you welding on the Driver board Colour:As Shown Material:Metal + Plastic Size: 15.5x4.8x3cm(6.11x1.89x1.18Inch) Debugging method: Method 1: the power amplifier with the generator 1KHZ adjust the volume of the power amplifier to the maximum, adjust the adjustable resistance, so that the meter points to the 0 position Method 2: No generator, you can use to download the generator software, use the to output 1KHZ to the power amplifier, adjust the power amplifier volume to the maximum, adjust the adjustable resistance, so that the meter points to the 0 position Package Contents: 1 * VU Meter Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.