What is it?
These plugs and switches are common in some parts of (Northern) Europe (Sweden, Norway, Germany etc). Everything is modeled to be physically correct and based on "real world objects".
There are 17 different types of outlets, with a earthed and unearthed version of each, plus 2 extra unearthed outlets. There are also 7 different types of switches (for now..).
There are also different versions of some of the objects, with minor differences.
The outlets are based on the so called "Schuko" (or CEE7/4) socket.
Structure (Names etc)
Each object is properly named and has it's own group with the same name. Since most of the switches has control objects, it might be preferred to import the groups (Blender should include the control objects if you just import the object for the switch, but it wont be grouped..) when you import switches.
Objects prefixed with an underscore can be ignored (they are used for the render).
In the .blend the layers is set up like this:
Layer 1: Render setup for the outlets
Layer 2: Render setup for the switches
Layer 11: All the earthed outlets
Layer 12: All the (standard) unearthed outlets
Layer 13: The two extra, unearthed, outlets
Layer 14: All the switches
Every object is positioned at the center and their origins are on the "wall plane" (where the object should touch the wall). The objects in the renders have the Subsurf modifier, but none of the objects you import do. In most cases you wont have any closeups of the outlets or switches, and so there's no need for subsurf.
Materials & Use tips
The materials is pretty straight forward and set up for Cycles. The plastic materials uses my node group called "ShinyShader", which is just a mix between diffuse and glossy (set up for ease-of-use). All white plastic uses the same material, even if it might not look like it in the renders.
Most of the outlets have pins that protrude through the "wall plane", but some outlets also have sockets that are recessed and so protrude through the "wall plane". For those outlets, you need to create a hole in the wall. It might be needed, but not necessary even for the outlets that aren't recessed (unless you do a closeup, you can get a way with, otherwise the result will look like my render in the example above).
There are two "contact sheets" included in the archive, one for the outlets and one for the switches. It's simply two images with all the objects (except the variations) and their names, so you easily can find the object that you want before importing.