The Bosch 3931A-PB features 4 modes of operation for maximum vacuuming versatility: -- Regular vacuum, Power Tool Activation, Pulse-Clean , Pulse-Clean with Power Tool Activation. Activation by power tool - Allows power tool's switch to turn vac on and off. 7-second run-on after power tool is turned off to clear hose of remaining debris. Power Broker Dial for allocating power (15 amps on a 15 Amp circuit, 20 amps on a 20 Amp circuit) between vacuum cleaner and connected power tool to optimize usage of the available power and avoid blown circuits. Also allows suction control for other purposes as well. Bosch exclusive Pulse-Clean electromagnetic filter cleaning system - shakes the dual filter cartridges to remove dust and maintain maximum suction power. Pulse-Clean can be activated manually, or automatically, when a connected power tool is switched off (a helpful remote control.)