| From The Devouring Fungus (Karla Jennings, 1990), chapter 6: — […] Imagine the frustration of the Stanford University instructor with an especially thick repairman who kept showing up to fix the same computer. He’d stay for a few hours, poke around, announce the machine fine, and leave; but he never knew what he was doing, so the instructor kept calling him back because the machine was never fixed. Finally the instructor got so mad that he said “Let’s do a binary switch. The problem has got to be one of the circuit boards.” The repairman didn’t know what a binary switch was, but he agreed because he had an angry customer. A binary switch involves taking half the circuit boards from the machine having trouble and switching them with identical boards in another machine. If the problem’s been transferred to the new machine, you know that something’s wrong with the switched boards. Then you reswitch smaller and smaller number of boards until you pinpoint which board is defective. They switched half the boards and, sure enough, the problem moved to the other machine. The repairman said, “So what do we do now?” So they swapped half of the changed boards. The trouble was that now both machines worked. (Perhaps shaking the boards around had put a loose contact back in place.) “That’s great!” said the repairman. “I’m going to use this procedure from now on. I never knew you could fix a machine just by swapping boards!” — |