= B =
Big Red Switch n.
[IBM] The power switch on a computer,
esp. the `Emergency Pull' switch on an IBM mainframe or the
power switch on an IBM PC where it really is large and red. "This
!@%$% bitty box is hung again; time to hit the Big Red
Switch." Sources at IBM report that, in tune with the company's
passion for TLAs, this is often abbreviated as `BRS' (this
has also become established on FidoNet and in the PC clone
world). 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.
--The Jargon File version 4.3.1, ed. ESR, autonoded by rescdsk.