Quick question

[PCMAD]

I want to know what this is on my powersupple fan,my old pc i had like i knob i could turn for the powersupple fan to run faster or slower and dont know what this is,

I havnt got a picture of it but looked on google for a random PS and found this picture

StarTech.com 300 Watt ATX Replacement Computer PC Power Supply Power supply - 300 Watt


What does that red button do underneath where you plug the lead in to.

Thanks

 

[Teny]

Are you talking about the switch that has the number 115 or 230?

If so, those are voltages. Some countries uses 115 and others uses 230. For example, I think US uses 115 and Europe uses 230 IIRC.