What's the black switch on the back of my psu?

[NaniBot]

I'm not talking about the red switch that's on the back of some psus. Mine doesn't have that. I'm talking about the switch that reads "o" on one side and "i" on the other. Currently it's on "i" and the pc works perfectly. I want to know what it does?

My PSU - Cooler Master Thunder 700w

 

[bob hays]

It turns off the power supply. If you turn it off your computer wont get any power and shutdown.

 

[EasyLover]

This black switch is used to power on or off the PSU. If it is in 0 position then power is off and your PC remains shutdown. If it is in 1 position then power is on and PC can be powered on.

It acts like on/off switch.

 

[danny2000]

They are international symbols set by International Electrotechnical Commission.
Wikipedia provides a good enough explanation for them> http://en.wikipedia.org/wiki/Power_symbol

 

[NaniBot]

Oh..Thanks!

 

[unplanned bacon]

As everyone else has says, it's main power for your system. O turns your PSU off and therefore no power to any components. 1 does the opposite