Radial Circuit using box installation method...

That diagram looks distinctly German - black for line and two-pin with scraping earth arrangement for the sockets,


There is a lot of variety of styles between countries - often one convention re-inforcing another over time - with little more than historical accident at the start of the divergence. European style sockets for example traditionally had a screw terminals where the wire was wrapped around under the screw head against a flat plate (a bit like on BS 951 clamps) rather than there being a "tunnel" - hence it was difficult to reliably terminate more than a single conductor in a socket terninal so junction boxes became the automatic way of doing things - even when using singles in conduit which looks bizzare to UK eyes. Once everyone was using joint boxes there was little need to "improve" the sockets to take multiple conductors, so the situation stuck. The UK on the other hand seemed to like tunnel terminals from an early date - which made shoving multiple wires into the same terminal easy and reliable - so as soon as the cost of the extra cable needed for 'looping in' dropped below the cost of a JB and the extra labour in installing it, looping-in caught on and joint boxes were mostly relegated to alterations and additions. The American had a similar problem to the Europeans, but they had more space in their back boxes - so ended up joining multiple conductors using "wire nuts" (screwits in old English) in the back of the box and just taking a single fly lead to the accessory - so a bit of a half-way house.


   - Andy.

That diagram looks distinctly German - black for line and two-pin with scraping earth arrangement for the sockets,


There is a lot of variety of styles between countries - often one convention re-inforcing another over time - with little more than historical accident at the start of the divergence. European style sockets for example traditionally had a screw terminals where the wire was wrapped around under the screw head against a flat plate (a bit like on BS 951 clamps) rather than there being a "tunnel" - hence it was difficult to reliably terminate more than a single conductor in a socket terninal so junction boxes became the automatic way of doing things - even when using singles in conduit which looks bizzare to UK eyes. Once everyone was using joint boxes there was little need to "improve" the sockets to take multiple conductors, so the situation stuck. The UK on the other hand seemed to like tunnel terminals from an early date - which made shoving multiple wires into the same terminal easy and reliable - so as soon as the cost of the extra cable needed for 'looping in' dropped below the cost of a JB and the extra labour in installing it, looping-in caught on and joint boxes were mostly relegated to alterations and additions. The American had a similar problem to the Europeans, but they had more space in their back boxes - so ended up joining multiple conductors using "wire nuts" (screwits in old English) in the back of the box and just taking a single fly lead to the accessory - so a bit of a half-way house.


   - Andy.