There was trouble with the relay. It was well designed, but there was doubt whether it would still be in working condition after ten centuries. Earl sent specifications to a jewelry manufacturer in Kansas City and had its moving parts made of synthetic ruby and platinum. The Cyberene _watched_ every step of construction--and so did Earl, from within his artificially created mental wall, careful not to reveal the huge holes he had knocked in it. With the arrival of the remade relay, Earl and Nadine entered the Brain, setting up a vibration-proof chasis in its innermost heart where the maze of fine spun glass was now a maze of yellowish threads containing a fluid with exactly the same properties as human nerve fluid. Outside, swarming over the catwalks and dotting the immense corridor circling the Brain, were dozens of technicians and experts, beginning the task of barraging the gigantic man-made brain with a never ending sequence of visual and audible sensory impressions which, according to theory, would eventually synthesize that miracle of creation loosely known as thought in the thousands of tons of glass and nerve fluid. Using a portable low power microscope and the techniques he had acquired during the months of work on the Brain in its construction, Earl attached motor buds to randomly chosen nerves, and sensory buds to others, attaching them to the transistors that would feed the relay, so that the action of the relay would set up nerve impulses in the Brain. When it had been done, he used sensitive detectors to make sure ion currents were generated in the nerves. Where those nerve impulses went to among the billions of "brain cells" didn't matter. All that mattered was that they went _somewhere_, so that the basic property of association would "hook them on" to the auditory impression created by speaking the code word or sequence of code sounds. "What should we use as the code sounds?" Nadine asked as their task neared completion. "I've been trying to think of something," Earl said. And in his mental prison Earl had been trying to think of the same thing, keeping track of his conscious mind's thoughts on the subject--even influencing them at times. It would have to be a sequence of sounds that stood no chance whatever of being spoken to the Brain during the next thousand years. Otherwise they might be spoken by chance and the Brain destroyed. "How about nonsense syllables?" Nadine suggested. Earl grinned. "Those are the most dangerous of all. Take Y.M.C.A. It's the initials of a huge organization. Any nonsense sequence of letters, no matter how long, might someday be the letters of some organization." Nadine frowned in bewilderment. "But what else is there? If we take any sequence of sensible words, they might be repeated in reference to something else at any time."