Battle of the bulge

Yet, in one regard, they are a nuisance. When attached to power supplies for laptops, they cause a lump in the side of the carry bag. Also, when made part of mobile phone chargers and placed in the pocket, they form an unsightly bulge and ultimately create holes. Plugs used in many countries are not as safe. US plugs, for instance, are small and flat, with only two flat pins and no fuse. Mostly, they have no earth pin, even when sockets have an aperture for one, and, when attached to a heavy current appliance, they often run hot – always a worry in a country where most houses are made of wood. Fires are a frequent occurrence. German system plugs, widely used in continental Europe, often only have two thin round pins and no fuse, although there is an increasing requirement for a couple of earth strips on the outsides. Plugs in India and Pakistan are more chunky, but usually only have two round pins and no fuse. But UK plugs have a fuse and three solid, rectangular section pins, all of which have to be present, in order to open the shutters in the sockets. The Challenge Our challenge this month is to come up with a way of making UK standard plugs in a form in which the pins don't stick out, but without compromising safety in any way. This means the pins cannot be made so they fold or are removable. They must remain solidly fixed to the unit. Yet, at the same time, the solution must allow them to go in the pocket without ruining it - or even in an envelope that can be pushed through a letterbox. The solution offered below solves the problem with some panache and at remarkably low cost. It has been developed to commercial form by a leading UK consultancy. We have tried it and it works perfectly; yet, to date, no one has expressed any real interest. For those without access to the web, the solution will be described fully in our October issue. Plug in and see if you have an even better idea. Solution The solution to this month's challenge comes from 42 Technology, based in St Ives, Cambridgeshire. Our illustration explains it all. The plug opens out flat, in such a way that all three pins go past each other. They are then held within the flattened enclosure, while remaining firmly and permanently attached to the faces of the plug, which now rest against each other in the folded form. In the samples we saw, the third earth pin is not connected to an earth cable, being designed for laptop power supply and mobile phone chargers that do not require an earth conductor, since they are double insulated.