# What do the "I" and "O" on the power switch stand for

#### ruyenopler

Joined Nov 7, 2022
4
There are two symbols "I" and "O" on most power switches

What do these two symbols mean?

#### ericgibbs

Joined Jan 29, 2010
16,792
hi r,
'I'= ON, '0' = OFF
E

#### SamR

Joined Mar 19, 2019
4,492
Think of the "I" as being a jumper to the power and the "O" as being Open therefore without power.

#### WBahn

Joined Mar 31, 2012
27,893
There are two symbols "I" and "O" on most power switches

What do these two symbols mean?
They represent the binary values zero and one, which are traditionally associated with logical "LO", "False", or "OFF" and "HI", "True", or "ON", respectively. In this context, they mean "OFF" and "ON".

#### MrSalts

Joined Apr 2, 2020
2,619
[Sarcasm]
They are in Latin
The Latin word for "on" is "in" = I
The Latin word for "off" is (conveniently) "off" = O
[/sarcasm]
No matter how many stories you may be told, the | is simply a line, and the O is simply a circle.
they represent "on" and "off". Many people remember which is which by other lessons they've learned in life but the phrase, "the standard is the standard" applies here - it is just a line, and a circle.
the standards are (yes, a standard for each line and circle)...
Power On (IEC 60417-5007)
Power Off (IEC 60417-5008)
There is also a statement from IEC to dispel any rumors that they are binary one and zero.

#### MrChips

Joined Oct 2, 2009
27,686

#### MrSalts

Joined Apr 2, 2020
2,619
View attachment 281371
The all inclusive version.
That is officially called a "standby" button in IEC or an alternative power symbol in IEEE.
IEC 60417-5009 stand-by symbol,
IEEE 1621 power symbol

#### nsaspook

Joined Aug 27, 2009
10,698

M.O.O.N, Moon!

#### JuliaSmith

Joined Nov 9, 2022
6
I=ON, O=OFF

#### AnalogKid

Joined Aug 1, 2013
10,176
Note that in post #7, images 3 and 4 are switches that must be mounted horizontally; that is, rotated 90 degrees from their orientation in the images. Pedantically (?), the I and O are symbols, not characters. As such, their orientation is part of their definition.

Just
- Like
- - The
- - - Schematic
- - - - Symbol
- - - - - For

GROUND.

ak

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#### AnalogKid

Joined Aug 1, 2013
10,176

#### nsaspook

Joined Aug 27, 2009
10,698
 A crescent moon, indicating sleep mode, is added by IEEE 1621 as a replacement for the standby symbol

#### maxpall

Joined Nov 24, 2022
1
I = On
O = Off
This is a confusing matter for me also. Whenever I see I and O it makes me confused. It should be easy for everyone.
I just see the colour Green= On and Red = Off. It's better than I and O.

#### xox

Joined Sep 8, 2017
794
Meh, maybe it's a bit old-school, but usually I prefer the ON/OFF duo as opposed to the dual-purpose (single) button. No good reason, really, just "feels right"....

#### Jon Chandler

Joined Jun 12, 2008
432
I just see the colour Green= On and Red = Off. It's better than I and O.
Industrially there are two schools of thought regarding green and red indications.

The first is:

Green = go (on)

Red = stop (off)

The other is:

Green = safe (off)

Red = danger (on)

It seems to break down by industry.

#### MrSalts

Joined Apr 2, 2020
2,619
The other is:

Green = safe (off)

Red = danger (on)

It seems to break down by industry.
A classic inversion if work / life imbalance. Then the employee takes this experience home and their spouse thinks they are complete idiots because they don't know the green light means the power is on.

#### MrChips

Joined Oct 2, 2009
27,686
Another school of thought:

A red button when pushed turns on the red light.
A green button is pressed to turn on the green light.

Now choose if red light means power is ON or not.

#### nsaspook

Joined Aug 27, 2009
10,698
The fad of using blue LEDs for power indicators solves the red/green indicator problem.