Sockets on Different Phases ?

[charles]

before harmonization, Germany used red for earth! The point about the earth wire is the sleeving is striped.

[Dave Plowman (News)]

They still do on cars. ;-)

Thing is that the inability to distinguish between red and green in poor light is pretty common among males. But then with everything coming with a fitted plug these days not the problem it once was.

[Steve Walker]

Ah, fair enough. But each indicator should be labelled anyway. Coloured indicators for each phase will still appear lit or not to a colour blind person, so noworse for them than them all being white.

Incidentally though, it is normal on many control panels for green and red lights to be used for running and stopped. Many people are red/green colour blind, so they have to look harder at labels.

On screen control systems often have devices or valves that are green for running or open and red for stopped or closed. I wonder how many operators are tested for colour blindness?

From the quick look that I've done. Good colour vision still seems to be required for apprentices, but not for people who work as electricians and may have gained qualifications and experience without being an apprentice.

SteveW

[newshound]

IIRC things like gyroscopes on post-war military planes ran on 400 Hz. My father bought me one in the 1960's which ran off a 12 volt rotary converter.

[newshound]

Sounds more like Economy 7 to me

[newshound]

I was involved in the design of some new control kit in the 2000's and the then mandatory Human Factors assessment lady more or less vetoed any coloured lights.

[Steve Walker]

She shouldn't have been doing. She should have been requiring other ways that a colour blind person could get the information (such as labelling), but not removing the best and quickest way for non-colour blind operators to get that same information. A red/green indication can be spotted from across the room, labelling and the like can't.

SteveW

[NY]

Ah the standard "a few people can't do it so we'll drag everyone else down to that level" approach of H&S, Human Factors, political correctness etc. :-(

[NY]

Before I went to university, I worked for a year off in a research chemistry lab where they did a lot of colour chemistry. My boss was telling me about my predecessor who kept getting results that no-one else could replicate. To begin with, the lad was just asked to repeat his experiments and still he was adamant about the colour changes that he saw. My boss decided to watch, to see if the lad was doing something different. Just as they were about to get to the colour-change part of the experiment, the lad said casually "I

*am* colour blind - does that matter?". Yes indeed it did matter: what the student was recording as a yellow to green change was actually the expected red to blue change.

As my boss was telling me this story, I thought he was going to say that the lad didn't know he was colour blind and this was how he first discovered it, but no - he already knew full well but didn't realise that it would be critical when doing colour chemistry.

[jrwalliker]

Not necessarily. I recently came across somebody who could not see red at all. It was a sunny day and a glass ornament was casting a clear spectrum on the wall. He pointed to the parts of the spectrum that he could see. Red was simply not visible at all.

John

[A_lurker]

Not a few people -- around 1 in 12 men are red-green colour blind. I'm not too severely affected, but I have great difficulty telling whether an LED indicator is red, orange, yellow or green; though I can usually see the change if I'm watching it. Flashing in a particular pattern solves it.

Wiring serial comms 'D' connectors was always a bit of a challenge, too.

[Dave Plowman (News)]

Figure an optician friend quoted for the UK was 1 in 3 males with blue eyes. Something to do with genes. May be different today.