Why did the UK change from round pin to square pin plugs?

Indeed, why I chose that word :-)

I was just highlighting that Animals claim was (at once time at least) true, even if it does not apply to the currently available adaptors.

BS1363-3 is the doc you would need (it deals specifically with adaptors of various sorts). I had a quick glance (it is quite a long doc) and can't see any specific requirement that they not be stackable. That may have been written into a standard in the past, or (more likely) it was just an industry agreement at one point.

Wall warts being one of the more troublesome devices to get into an adaptor...

In addition to the mechanical problems, there is a potential problem with lots of cascaded connections - the fault loop impedance tends to climb, and there may come a point where you can no longer clear a fault reliably because the accumulated extra contact resistance has crept up too much.

Modern switch mode ones tend to be smaller than older linear ones. Sometimes just finding one with the right form factor which matches the electrical requirements is the way to fix the problem rather than accommodating the supplied unit when it does not want to fit.

You could stack more adapters to form legs to support the structure from the floor ;)

Do they tell the same lies as you, Wodney?

Thought you knew how to use usenet, etc. You lied about that too, then?

In the early days of rings, one per house was the norm. And I did say 'a' ring. ;-)

Some things are really not worth discussing in detail. Either you've played trying to stack adaptors or you haven't. I have. I expect most of us have. And yes, as said things have moved on since. There's a lot more noncompliant stuff around now.

The springing arrangement of round pin plugs was a disaster. The 1363 system is much much better in that respect. It also prevents putting the plug in at an angle and getting fried by the exposed and now live pin. The round pin system must have seemed like a good idea when introduced, but it degenerated into a carcrash. I guess it was a move forward from the previous 2 pin system, but it turned out to be a long way from satisfactory.

... often on 4 fuses

You never could bullshit your way out of a wet paper bag.

So are you saying that adaptors with a socket on the rear face (which would allow stacking, subject to there being a big enough stand-off to accommodate the cable of a plug) are non-compliant? If so, fair enough. Maybe the original design standard specifically outlawed that arrangement.

It looks as if you made the original statement about square pin being designed not to stack, but now can't be bothered to substantiate it, instead falling back on "come back to us when you've played with adapters" and "Some things are really not worth discussing in detail. Either you've played trying to stack adaptors or you haven't."

I think I've found an example of adaptors which will stack, and have explained why. You can't be bothered to explain why I'm wrong - if I *am* wrong. Frustrating. Stalemate.

Okay, thanks. I got the terminology wrong.

From a position of lack of any expert knowledge, I still think if I lived in Denmark and I wanted 10 sockets in my kitchen, rather than just lining them up as a radial, I would want to connect both ends. Just out of habit I suppose.

I suppose fault-finding would be easier with a radial circuit as a ring could continue to operate with a broken connection.

You could do, but there would only be marginal benefit.

You would get the slightly better fault tolerance, and higher integrity earthing (handy for circuits which anticipate high earth leakage currents), but the main benefit of much greater circuit capacity won't be there since you will won't be able to increase the circuit breaker to

The pros and cons are nuanced. Each circuit type has situations where it will do better than the other. For general purpose socket circuits I would argue that the benefits of ring win over radial in most cases. Here is a description of the differences:

I am not aware of any actual standards *requirement* to make them unstackable. It may be in the past there was one, if so it would be interesting to see a citation. It may be there was an informal industry agreement.

The mechanical packaging will often dictate that there are offsets in the positions of the sockets and pins that can make not all the obvious stacking positions work in practice - although quite often that only applies to the first one you stack. Additional ones get easier!

Here is a "compliant" adaptor which I think I have had for 40+ years (I used to use it to plug in my VIC-20 and portable TV on the same socket):

Armed with a selection of adaptors with different layouts, your options for excessive stacking increase.

Yes, I sense a certain amount of obfuscation and deflection here :-)

You are not wrong, although as Animal alludes to, stacking them is not always as easy in practice as it sounds like it ought to be in theory.

I can no longer find the papers for, and note of the discussion at, "The Great Debate: Ring circuits versus Radial circuits" at the IET in 2007. But IIRC even they did not address what I consider to be the primary argument against the British system: the pain of standing on a 13A plug when it's on its flat back.

Some of this article was inspired by that paper IIRC:

It goes further than that, to the overall system design. Having 3 types & ratings of plug & socket with items that are often moved around the house is a recipe for misfusing & mis-plugging. I guess it sounded sensible before anyone had more than one appliance, and it wasn't portable.

No I'm not saying that.

correct. Life is far too short to talk minutiae with people that cant be botherd to inform themselves. If you have an opinion of me for that, I won't worry about it.

You can't force everyone to talk in detail about what you want. Such is life.

Yes, there are minor differences. But there is one major one, the fact that a ring with a bad connection is still safe. A radial with a bad connection may catch fire.

I was hoping that I was about to learn *why* round-pin socket adaptors could be stacked indefinitely, to dangerous levels (electrical overloading; weight of plugs pulling adaptors apart), whereas square-pin sockets couldn't. I was intrigued. I'd always thought that round- and square-pin adaptors were topologically the same: a rectangular block with the relevant type of pins on one side and several sockets which accept plugs with the appropriate pins on some of the other sides.

Sadly you weren't prepared to back up what you said: the tone of your statements implied that you knew the answer but weren't prepared to divulge it.

Yes, I could go out and buy lots of adaptors that I don't actually need (assuming I could find ones of the type that I posted photos of) and see whether I encountered a problem with greater levels of stacking, whereby sockets on some adaptors blocked those on other adaptors. I *think* it's the blocking of one socket by another which is what you are alluding to, but I don't *know* because you won't damn-well explain yourself. The tone of your "come back to us when you've tried it" suggests that you know the answer but don't want to share it.

Life's too short to deal with people who make sweeping statements that they won't substantiate. I have formed an opinion of you which isn't favourable, but I know that's no skin off your nose. We just have different ways of looking at the world and of challenging statements that *seem* not to be true. Everyone's different - thank goodness: it would be boring if we were all the same!

As a matter of interest, what do other people on the thread think? Am I being unreasonable in asking Animal to explain his intriguing round-versus-square generalisation? Is he being unreasonable in not wanting to go into details, whilst giving the impression that he knows the answer but isn't prepared to discuss it?

I have "square pin" adaptors that can have another one plugged in, etc. I also have 4 way (& 6 way and 10 way) strips which will another one to be plugged in.

I also have 15A round pin adaptors (from a theatre requirement) which allow

Every house I've ever lived in or visited has had square-pin sockets, either because it was built after BS-whatever came into effect or else because it was old enough that it needed to be rewired and at the same time the sockets were changed. I've seen a few old 5- and 15-amp plugs, but I've never actually seen an adaptor.

I remember when I was helping with the lighting for a school play in 1980 when I was in the 5th Form, seeing round-pin plugs on all the stage lamps. "Why were those still being used?" I asked. The sixth-former who was in charge grinned and said "Would you fancy getting on a ladder in the middle of a performance to change a blown fuse on a light above the stage? The penny dropped!

The lighting gantry was very old: each circuit had a fuse-wire fuse (no MCBs in sight) and all the dimmers were 2-foot-long wire-wound rheostats with big Bakelite sliding knobs. There was a fan constantly blowing on the rack of rheostats to keep them cool, and there was a length of wood used to operate multiple faders at the same time. The skill was in planning the mapping from light circuit to rheostat, using the patch panel, so as to put circuits that we'd wanted fading at the same time on adjacent rheostats to allow the wooden bar to be used. At several times during a performance, we had to change the patch mapping if different sets of lights needed to be faded simultaneously.

The really scary thing was the wire-wound fader for the house lights. The total lighting load for the house lights was about 25 kW. This was fed by a large metal box about 3 feet square with lots of ventilation holes in it, and with a big hand-wheel to move the sliding contact. Turning that handle made a loud graunching, screeching noise. We were warned to fade *quickly* and never to leave the contact in a half-completed position, only fully "open" or fully "closed". The lighting gaffer showed us why: with the fader half open, the windings glowed cherry red within about 10 seconds...

The irony is that the school also had a modern lecture theatre that was equipped with banks of fluorescent house lights that could be dimmed, and lots of theatrical lights. All the dimmers were small sliders on a desk in the projection room, which controlled racks of solid-state triac dimmers. The house-light one made an angry buzzing as it was dimming, and sometimes cooling fans would come on, but it was nice and easy to operate: you could sit at a desk, with a lamp shining on your script, instead of perching on a gantry 10 feet above the wings, sweating and doing everything by feel. With its nice tiered seating, it seemed the ideal place for stage plays. The only problem was: the lecture theatre was built without wings and a proscenium arch, so the only way actors could make their entrances and exits was via the two fire doors that lead to the playground outside. So the school hall was used instead for plays.

I never managed to work out how the hell you can dim loads of standard

Interestingly, modern dimmable LED lamps (whether driving from a trailing-edge triac dimmer switch, or from internal circuitry within a Philips Hue bulb) have the same problem of a fairly high minimum brightness: they will only dim so far and then they go out completely.