Almost all appliances, lamps and sockets
Just come with a power switch
There will inevitably be "|" and "O" two symbols
If you only look at the symbols to judge
“|” What does "O" really mean?
You can also tell which is the circuit connection
Which is the circuit disconnection?
Many people think that "O" is powered on, "|" It's a power outage
Because the English open is OPEN
Many switches use ON/OFF to represent on and off
“|” and the "O" symbols
In fact, it is the two letters of "I/O" in English
is an abbreviation for input/output
Translated is input and output
So, of course, "|" It is powered on, and "O" is powered off
The above points all seem to make sense
But all are incorrect explanations
It was really during World War II
In order to ensure the stable operation of electrical equipment
Engineers need to develop a common set of standards for electrical equipment
Unify the navy, army and air force and civil defense
Electrification equipment in various fields such as logistics
The standard of switching and rotating toggle switches
In particular, the identification of the switch
It only takes a few minutes of training to guarantee
Soldiers from different countries
And maintenance workers can identify and use it correctly
An engineer came up with a simple solution
That's the international binary code
Since the "1" in binary means "on"
"0" means "Closed"
So, there is a "|" on the switch. and "O"
Later the International Electrical Engineering Commission (IEC)
In the technical specifications prepared in 1973
Formal proposal to "|" and "O"
As a sign of a power supply on-off cycle
China's national standard GB 15092 is also clear
The circle "O" represents the circuit disconnection (i.e. "turning off the lights")
Straight bar "|" Represents circuit closure (i.e. "turning on the light")
Source: Popular Science China