This is 808nm infrared semiconductor laser with adjustable power supply.The output power is 7W, you can adjust the power by adjusting the size od current. The adjustor is for changing the current thus laser power. The current value is showed on the panel. The knob should be tuned gently and smoothly. You can lock the knob by the push switch on side of the knob.
Warning: 7W is ultra high power laser, we must wear safety goggles when operating.