Cal smiled at the directions again. He envisioned the years of experimentation that had gone on with no results. The directions told why. Without them, its operation was impossible. And yet it was so simple. The idea of owning contraband bothered Cal. It belonged to the Interplanetary Museum, by rights. It would be returned. Of that, Cal was definite. But some little spark of curiosity urged him not to return it right away. He would return it, but it had been gone for several years and a few days more would make no difference. He was far from the brilliant scientist--any of the engineers of the long-gone Venus Equilateral Relay Station would have shone like a supernova against his own dim light. But he, Cal Blair, had the answer and they did not. But it was more to prove the correctness of his own ability as cryptographer that he took on the job of making the little Key work. The job took him six weeks. An expert electronics engineer would have done it in three days, but Cal had no laboratory filled with equipment. He had neither laboratory technique nor instruments nor a great store of experience. He studied books. He extracted a mite of information here and a smidgin there, and when he completed the job, his equipment was a mad scramble of parts. Precision rubbed elbows with sloppiness, for unlike the trained technician, Cal did not know which circuits to let fly and which circuits needed the precise placing. He found out by sheer out-and-try and by finally placing everything with care. The latter did not work too good, but continuous delving into the apparatus disrupted some of the lesser important lines to the point where their randomness did not cause coupling. The more important lines complained in squeals of oscillation when displaced, and Cal was continually probing into the gear to find out which wire was out of place. He snapped the main switch one evening six weeks later. With childlike enthusiasm he watched the meters register, compared notes and decided that everything was working properly. His testing equipment indicated that he was operating the thing properly--at least in accordance with the minute engravings on the side. But with that discovery--that his rig functioned--there came a let-down. It was singularly unexciting. Meters indicated, the filaments of the driver tubes cast a ruddy glow behind the cabinet panel, a few ill-positioned pilot lamps winked, and the meter at the far end of the room registered the fact that he was transmitting and was being detected. It was a healthy signal, too, according to the meter, but it was both invisible and inaudible as well as not affecting the other senses in any way. Now that he had it, what could he use it for?