Will switch the dust extractor on when attached to the machine. The unit is fastened in a convenient position and plugged into a 13amp outlet socket. The extractor and machine tool are both plugged into the auto switch box. When the machine tool is switched on the extractor is automatically switched on. When the machine is switched off the extractor continues to run for a short time to remove residual dust. Resettable overload protection rated at 13amps.