This is a very convenient factor when working with AC powered devices that produce a lot of dust, such as B. Table saws, miter saws, routers, etc. The device will automatically start the vacuum cleaner when detection, turn on the saw, and then automatically turn off when the power is turned off. This eliminates the need to remember to turn the vacuum on and off. Without this device, I often forgot to turn on the vacuum until mid-cut, which was then too late, or turn off the vacuum after the cut, wasting energy and creating unnecessary noise. . This instrument is easy to use and a must have in every workshop. Highly recommended for its size and convenience.