Abstract: An electrical switching device for use on machinery to prevent machine operation unless safety guards or the like are correctly positioned comprises two separate parts one part including at least two Hall effect devices which respond to magnetic poles of opposite polarity and electronic switching means which is actuated only when all the Hall effect devices are triggered simultaneously, and the other part including a corresponding number of magnets positioned to actuate the respective Hall effect devices when the two switch parts are placed in close proximity and predetermined orientation. The switch is substantially tamper proof and a control circuit can detect any unauthorized attempt to override the switch.