big red switch 

Switch that completely de-energizes (or kills) a device. From early IBM PC's which had a Big Red Switch on the side connected to the main power feed.

It's out of control -- hit the Big Red Switch!!!!

big red switch by Anonymous March 30, 2003

Big Red Reset Switch 

The main power switch, often on computer equipment but applicable to any piece of equipment. Used to stop the system when all other control inputs have failed, often because of a system crash or lockup.

Tech 1: "Buggeration, we have the Blue Screen Of Death yet again !"

Tech 2: "Shit. Give me a sec, I shall apply my digital extremity to the Big Red Reset Switch"

<Click>

<Click>

Tech 1: "Ok, it's rebooting now".

Big Red Reset Switch by eighth of seven February 6, 2010