up is on or up is off? .....

[Jim GM4DHJ ...]

do you think the merrycan way of switching with down off is more sensibubble that what we do in the uk ?

[Jim GM4DHJ ...]

I know it is harder to accidentally knock things up than down ......or is there another reason?

[Harry Bloomfield]

Jim GM4DHJ ... has brought this to us :

We have several opposing conventions. MCB's and CU main switches are up for on. Only (1w) wall switches a down for on.

[alan_m]

Two way switching uses both conventions.

Up/down os probably only really seen with older tooggle knobs on switches. Most of us probably use sockets/switches where pressing the lower part is on and pressing the upper part is off.

I once worked on a rack of equipment where the (military) customer specified that a big red illuminated front panel light meant the power to the electronics was off! Guess how much damage was caused to plug in boards that didn't like to be hot plugged?

[whisky-dave]

There was an old expression of getting a girl knocked up which meant getting her pregnant.

[Graham.]

I see that as the same action, the latter having a modified toggle.

Someone told me that strictly speaking American three pin sockets should be mounted with the earth pin down, but this is universally ignored to make them look like a face.

I think they also mount them sideways in architraves.

We never (well hardly ever) mount our sockets otherwise than earth pin up, but I have more than one Chinese wall-wart with labeling affixed in an orientation that suggests some people in China think our sockets are earth pin down.

[Steve Walker]

I have worked on designs for many oil and gas/chemicals companies. Most have wanted a green light for say a pump running ok and red for stopped or failed, but some wanted the reverse, as they reasoned red for energised and green for deenergised and therefore safer. A few even wanted a mix, with green being for fail-closed valves that were in the open position and for fail-open valves in the closed position, thus showing their energisation rather than their positions.

SteveW

[Andy Burns]

Plessey ISDX is similar, a white bulb which is barely visible through the slits in the case means power has failed ...

[newshound]

I worked on a (nuclear) project with a lot of C&I in the noughties, the designers initial design followed the green for good, red for bad convention. However, when the mandatory Human Factors specialist came in she insisted that only white lights were used.

[Tim Streater]

Why?

[Dave Plowman (News)]

At one time, Crabtree sockets had their rocker switch flush when off. Raised on. Which meant bashing it with a chair leg or whatever meant it could only be switched off. Seemed quite sensible to me.

[NY]

Maybe because people with red/green colour-blindness wouldn't be able to distinguish between the two. If so, it's a classic case of dragging everyone down to their level: make everyone suffer from "can't distinguish" between two white lights for the deficiencies of the minority.

By all means have "ON" and "OFF" on the lights, or different shapes of light, but don't throw away colour just because some people can't use it.

[newshound]

I think that is one of the reasons, IIRC another is that, as with the valve example quoted earlier, the reality is that people can sometimes interpret the colours differently. For example, for a valve is green "open" and red "closed"? Or is green "normal" and red "fault condition"?

It is some while since I had the discussion, but in fact the expert made a very sound case, including some clever but real life examples. The argument is that it is better for people to pause to think about an indicator, and to read its markup before taking action.

This is not to say that colours are not acceptable for separate things like fire, gas, or other emergency alarms. In the civil nuclear industry, the primary alarms are audible rather than visible: continuous for "Fire" and intermittent or warbling for "Nuclear". Visual beacons are needed for areas with high noise levels, though. The lights are positioned in a stack, always in the same order, so that the colourblind can always interpret them correctly.

See above.

[Max Demian]

A green traffic signal should mean stop as green is a calm colour. Red is fierce and should mean go.

Green chillies tend to be hotter than red ones, so the hot tap should be green and the cold one red.

[Clive Arthur]

Cold makes you turn blue, and hot makes you turn red.

But...

The Earth is blue, while earth is usually brown or black, live things are often green and a green/yellow thing would probably be poisonous, white or grey is neutral.

Cheers

[whisky-dave]

Is this why hospitals tend to have sockets without a switch so they can't accidently be switched off ?

[Jethro_uk]

Except ISO (?) guidelines from long before that (certain in play in the

1980s) was that in any control system, a change of status should never be signalled by a colour change *alone*. It should be augmented with either an audible warning (buzz or click) or a flashing to draw the attention.

I think railway signalmen were onto that over a century previously, no ? Railway signals using a colour *and* position to indicate status.

[Jethro_uk]

I do recall something about aircraft switches being oriented so that switches are on when down, to avoid being accidentally switched off due to weakness, gravity and vibration.

[S Viemeister]

In the UK signs for emergency exits tend to be green - in the US, they're red...

[Brian Gaff]

Depends, we have done both over here. If you extended a toggle from the flat of a rocker light switch up would be on, but on the other hand are you really likely to be falling past a switch with the presence of mind to switch it off which ever way it was?

Brian