I came across a wonderfully counter-intuitive piece of user interface design this week.
The room I was in had a sliding shutter (that, for reasons best known to the architects, opened into the main building and not outside). The two halves of the shutter are controlled independently – that is, you can close one side or the other, or both. Each shutter is controlled with independent switch panels.
Common sense would suggest a single rocker switch: pushing one side would close the shutter; pushing the other would open it. The designers, however, had other ideas and selected the implementation below:
Each shutter has a pair of single-action switches – one to close the shutter (the one at the top) and one to open the shutter.
Pressing the top switch (on its right hand side) closes the shutter – as expected.
Pressing the bottom switch on its left hand side (the intuitive action) does nothing. In fact, you have to press the bottom switch on its right hand side to get it to do anything.
Even better, the switch panel for the right shutter is an exact copy of the the left; so the controls are completely opposite – the top switch opens the shutter, the bottom switch closes it!
As they say: good design is like oxygen – you don’t notice it until it’s not there.
Glennan is an embedded systems and software engineer with over 20 years experience, mostly in high-integrity systems for the defence and aerospace industry.
He specialises in C++, UML, software modelling, Systems Engineering and process development.