A method and system and associated circuitry for controlling and stopping the motion of dangerous moving parts such as power saw blades substantially instantaneously in response to body or human capacitance produced by an operator coming with a predetermined critical distance from the moving part. This method includes, and this system provides for, among other things, connecting an antenna to the moving part and then coupling a tunable circuit to the antenna so that the antenna provides a variable lumped capacitance parameter (dependent upon human body capacitance) within the tunable circuit. This lumped capacitance parameter is variable in response to body or human capacitance produced when an operator comes within a predetermined critical proximity to the moving part. This variation in lumped capacitance serves to tune the circuit at or near a point of resonance to thereby enable an RF signal to pass through the tunable circuit at a detectable level which is subsequently processed to activate safety equipment for controlling and stopping the motion of the moving part substantially instantaneously. This invention is also adaptable for use with non-dangerous mechanical apparatus such as automatic door openers, automatic robot equipment, and capacitance-sensitive lighting appliances, and the like. It is also adaptable for use on automobile safety equipment, such as the proximity sensing of persons approaching an automobile out of the normal line-of-sight vision angles of the driver.