Volume Controlers?

I just started with my pilote project for my master, and as a part of this I am colecting symbols from warius machines and categorising them.

Take for example the volume controls, why are there so many variations for such an easy thing? They all represent the same action whit different symbols and shapes. Some more unlogical than others. Take for instants the two dots on the right side, Is the full circle more or is the empty circle more?

Why is it like this? Why can’t they all use just one type of standard shape/symbol? 

Can you tell me why? Or would you like to tell me witch symbol you think is the best?

Public symbols and pictograms

Public signage/warnings and pictogram’s are a great sourse of inspiration. It’s a visual language that is meant to be understood by people all over the world. Take for instance these arrows, they communicate a direction without the need of language/words.

Toilet sign is a example of a sign/pictogram that is well known and comes in many variations. 

Other signs you might newer have seen before, but still you can understand them.

 

These are typical danger/warning pictogram’s telling you about various ways of dying or deforming your body. No language needed except for the visual.

You can get instructions by a series of pictogram’s, that for example enables you to operate this japanese fire extinguisher.

Most of the pictogram’s you See on a daily basis are usually simplistic. But sometimes you come across more advanced ones.