chicken switch

chicken switch  {n.},  {slang},  {Space English}

1. The emergency eject button used by test pilots in fast and high flying aircraft by means of which they can parachute to safety if the engine fails; later adopted by astronauts in space capsules.

Don't pull the chicken switch, unless absolutely necessary.

2. The panic button; a panicky reaction to an unforeseen situation, such as unreasonable or hysterical telephone calls to friends for help.