What Do Power Button Symbols Mean?

Power StatesPower States

We often ignore the simpler things in life, just like the power buttons on our daily-use technology. Have you ever wondered why the power buttons on all gadgets, technologies, and items are the same, even though they are from different manufacturers?

3 power buttons
Power buttons with different symbols

If you have, then you have come to the right place. Let us tell you the story behind the power button symbol, and why it is what it is.

What is power symbol?

The circle and line symbol, often called the universal power symbol, shows whether a device is on and functioning (circle and line) or off and not powered (just the circle).

Let me explain this in further detail:

  • The Circle and Line Symbol

    Circle and line power symbol
    Circle and line power symbol

    This symbol is a common representation in technology and electronics. It’s often seen as a circle with a vertical line inside it. Think of it like a simple drawing of an ‘O’ with a straight line through the middle.

  • Universal Power Symbol

    Universal Power Symbol
    Universal power sign

    This term refers to the fact that this symbol is recognized internationally and universally as an indicator of the power status of a device. Whether in Europe, Asia, or the Americas, you’ll likely encounter this symbol and understand its meaning.

  • Device Powered On and Working

    Power button is lit thus device is on
    Power button is lit thus the device is on

    When you see the circle and line symbol lit up or displayed, it means the device is active and functioning correctly. For example, your computer screen displaying this symbol indicates that your computer is turned on and ready for use.

  • Device Turned Off and Not Powered

    Circle without line
    Off-state power button

    When you only see the circle without the line (meaning the line isn’t lit or displayed), it signifies the device is turned off and not receiving power. It’s essentially in a standby or off state. For instance, your TV might display this when it’s turned off but still connected to a power source.

Why is a symbol necessary for power buttons?

Well, for one reason, it’s obvious that it was necessary to mark the power buttons so that a person will know what function that particular button will do. It could be dangerous when a person does not know what the function of the button is, and they could accidentally power it on or off which could result in someone getting injured.

There was a need to develop a universal sign that could be understood by everyone around the world. It would have been much simpler to write On/Off on the buttons, but not everyone around the world understands English. It could also get a little confusing, and a person could have difficulty reading the signs, even if they knew English.

on off inverted
Rocker switch with on-off indication

To avoid any mishaps, an international committee known as the International Electrotechnical Commission (IEC) was handed the responsibility to create a symbol that could be understood by everyone around the world. In other words, a new “standard” was to be implemented, which was to be followed by everyone.

How the I and O power button symbols were created

The IEC decided that the symbols to be used for power on and power off would be “I” and “O,” respectively. The “I” represents the binary 1, meaning on, whereas the “O” represents the binary 0, meaning off.

The binary number system was understood by almost everyone worldwide and meant the same in every language. Moreover, it would not be confusing for the people even if the button was turned upside-down or rotated in any direction.

This factor was important to consider as the light switches in the US are in the up-position for on and down-position for off. In contrast, many other parts of the world have adopted the opposite, i.e., the up-position for off and the down-position for on. Using the “I” and “O” symbols, it would no longer be a problem for individuals to know which way is on and which way is off, regardless of which part of the Earth you belong to.

Understanding the different power button symbols

Understanding power symbols Opt
Understanding power symbols

Even though the IEC had agreed to use certain symbols, why are there variations in it? This is because they had standardized different symbols for different types of buttons. Let’s dig into them a little deeper.

IEC 60417-5007 – Fully powered on state

This standard is used for the power-on symbol, which is a simple “I”. This marks a button or a toggle switch (rocker switch) to indicate that it is in a fully powered state.

fully powered state
IEC 5007 & IEC 5008 rocker switch

IEC 60417-5008 – Complete power off state

This standard is used for the power-off symbol, which is a simple “O.” Using this control will mark the device as “off,” and there will be no power. This, too, can be found on rocker switches.

off 1
IEC 5007 & IEC 5008 rocker switch

IEC 60417-5010 – Temporary On state

This symbol is usually found on the buttons used to turn off a device and switch it on by toggling them. A simple line within a circle depicts the symbol.

When the button is pushed, the device is powered on and when the button is released, the device powers off.

IEC 5010 button symbol

IEC 60417-5009 – Not fully disconnected state

This one is the most common symbol used all over the world. It is depicted by a broken circle with a line in between the two broken ends. Initially, this symbol was used for the “sleep” state, where the power is not fully cut off to the device and is in a low-power state.

partial cirlce
IEC 5009 button symbol

However, later the Institute of Electrical and Electronics Engineers (IEEE) intervened and said that this symbol is to be used for single buttons to toggle between the off state and the on state of a device. They also introduced a new symbol to illustrate the “sleep” state.

Crescent moon

The IEEE then introduced a new shape for the “sleep” state, the crescent moon. Using this control would put the device in a low-powered state. However, this symbol did not catch on much with the general public.

Sleep-state symbol: Crescent moon

Closing words

With these standards set, it is now easier for everyone to understand which way the button is on and which is off. However, all computers now come with a power button with an IEC 60417-5009 standard. Pressing the button once for a short period of time, if the device is on, will put it to sleep, and a long press will shut it down.

This is because the two international bodies agreed that the same symbol might be used for both purposes, and that is why the same button can be used to perform the “power on/off” function and put the device to “sleep.”

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Subhan Zafar is an established IT professional with interests in Windows and Server infrastructure testing and research, and is currently working with Itechtics as a research consultant. He has studied Electrical Engineering and is also certified by Huawei (HCNA & HCNP Routing and Switching).

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