Have you seen the power icon design closely?

You know the expression: the best design is the invisible one. And as cliché, as it might seem, we all tend to agree on it.
Even designers — who are curious and attentive people — see everyday objects without taking a second good look at them.
A great everyday example is the power button or better yet, the power symbol. Have you ever consider why is it like the way it is?
Why is it a circle and a line? And why are those two elements in that specific position?
Everywhere you go, the symbol has either the same representation or some part of it. But why?

The origin of the power icon

The power icon appeared for the first time in 1973, in the International Electrotechnical Commission’s Graphical symbols for use on equipment.
Before that, buttons used to have On and Off written indications in English, which could cause language barriers and weren’t very clear regarding the state of the button and the power mode.
In order to avoid confusion and having both globalization and technological evolution in mind, four different symbols were designed: 1) the power-on symbol, represented by a line; 2) the power-off symbol which is a circle; 3) the standby symbol that we commonly refer to as the power symbol, and 4) the power on-off symbol that is represented by a line inside the circle.

Power icon meanings

Each of these symbols represents different states of power on a device. The line simbolizes a fully powered state while, on the contrary, the circle means that the machine will be disconnected.
The combination of both symbols can represent the state of low power or what we commonly call turning on and off, or it can represent the variation between fully on and off (completely shut from the system).

But what the heck does it mean?

The reason why I believe that this graphical system has been so well-designed has to do with how we, as humans, visually think and communicate.

Let’s think about this design in terms of interpretations and meaning.
The circle is a closed shape. It doesn’t have a defined beginning or end when it’s fully closed. So it’s most likely that we associate it with something definitive, that started and finished.

The line is a path between two points: one is the starting point and the other the endpoint.
Contrarily to the circle, the line doesn’t have an end. It can be stretched out infinitely and therefore, we associate it with something temporary. The line starts at some point, but we don’t know when or if it’s ending.

When combining these two ideas we can have the outcomes that we’ve seen before: if the line cuts through the circle, the power state is only temporary, so it doesn’t cut off from the source entirely. On the other hand, if the line is inside the circle, it stays fully closed, which means that the action is completed. Once you’ve shut down the machine, it’s entirely cut off from power.

Making sense of the symbol

The rationale behind the design of the power symbol is quite something. Apparently is something so simple and insignificant, yet is very complex if you deconstruct its meaning.
This example just goes to show that great design doesn’t need to be bold and obvious. It’s true in all aspects of life, even the smaller ones.