Abstract: Hazardous electrical shocks are prevented in an electrical system, such as a swimming pool lighting system having submerged pool lights, by periodically testing for all potential hazardous electrical shock conditions associated with the system and blocking electrification of the system in response to the detection of any shock condition.

Abstract: Methods and apparatus for cutting a workpiece with a cutting tool rotated relative to the workpiece by an electric drive motor and advanced in that workpiece by an electric tool advance. These methods and apparatus sense obstacles to cutting in the workpiece by sensing an increasing draw of electric power of the electric drive motor in rotating the cutting tool relative to that workpiece, and automatically slow down the electric tool advance in response to such increasing draw of electric power. Such slowed-down electric tool advance drives the cutting tool to cut through the sensed obstacle in the workpiece. The speed of the slowed-down electric tool advance is automatically restored in response to a decrease in the sensed draw of electric power of the electric drive motor in rotating the cutting tool relative to the workpiece, and the cutting tool is advanced in the workpiece with the electric tool advance at the restored speed.