Having been affected by earth fault accidents, the author put together this little circuit. It consist of just three elements: the neon with its original resistor for example, salvaged from the switch on an AC power bar and a small capacitor (class Y) salvaged from the electronics of a low-consumption lamp. A larger capacitance makes the neon glow brighter. All this for no money at all. The neon lights only when there is an efficient Earth present. This works well at the author’s home, with Live or Neutral either way round. In the Elektor laboratory based in The Netherlands, some concerns were expressed as described in the June 2011 issue [1], as the circuit was sensitive to the relative positions of the Live and Neutral. So the Earth fault detector can also be used as a Phase detector, but probably in Belgium only. . The whole thing can easily be incorporated into a power socket; the author used a small transparent cove...