(BRS) IBM jargon for the power switch on a computer, especially the "Emergency Pull" switch on an IBM mainframe or the power switch on an IBM PC where it really is large and red. "This [email protected]%$% bitty box is hung again; time to hit the Big Red Switch." It is alleged that the emergency pull switch on an IBM 360/91 actually fired a non-conducting bolt into the main power feed; the BRSes on more recent mainframes physically drop a block into place so that they can't be pushed back in. People get fired for pulling them, especially inappropriately (see also molly-guard). Compare power cycle, three-finger salute, 120 reset; see also scram switch.