Regulars will already be familiar with the diagrams of U.K. systems posted in the Technical Reference Area. I asked Nick (who converted my original rough sketches into the CAD line drawings you see) to add the TN-S, TN-C-S, and TT designations that those of you in Europe will be familiar with.

Thanks to Nick and to Scott35 for re-posting these diagrams. You can see them here .

All three of the systems are still in common use in the U.K., TN-S in older urban areas, TT mostly in rural areas, and TN-C-S (PME) almost everywhere now (originally only in certain rural areas).