Many power tools have activating switches that shut off power to the tool when the switch is released. Drills, saws, mowers, hedge trimmers, grinders, and other power tools have such controls. The switch that activates the tool action must be depressed at all times during use. If the operator leaves the operator position or lets go of the control, the tool stops. There is little chance of injury to the operator. For some tools, like mowers, standards require that the action of the tool stop within a certain time. This prevents the user from moving to a position of danger while the dangerous part of the machine is still in motion or coasting to a stop.