The Three Moons came next, and then Don began to sketch. "Suppose we make a driver tube like this," he said. "And we couple the top end, where the cathode is to the input side of the relay tube. Only the input side will require a variable-impedance anode, coupled back from the cathode to limit the input to the required value. Then the coupling anodes must be served with an automatic-coupling circuit so that the limiting power is passed without wastage." Barney pulled out a pencil. "If you make that automatic-coupling circuit dependent upon the output from the terminal ends," he said, "it will accept only the amount of input that is required by the power being used from the output. Over-cooling these two anodes will inhibit the power-intake." "Right," said Wes. "And I am of the opinion that the power available from Sol is of a magnitude that will permit operation over and above the limit." "Four million tons of energy per second!" exploded Walt. "That's playing with fire!" "You bet. We'll fix 'em with that!" "Our experience with relay tubes," said Farrell slowly, "indicates that some increase in range is possible with additional anode-focusing. Build your tube-top with an extra set of anodes, and that'll give us better control of the beam." "We're getting farther and farther from the subject of communication," said Channing with a smile. "But I think that we'll get more out of this." "How so?" "Until we get a chance to tinker with those tubes, we won't get ship-to-ship two ways. So we'll gadgeteer up something that will make Terran Electric foam at the mouth, and swap a hunk of it for full freedom in our investigations. Or should we bust Terran Electric wholeheartedly?" "Let's slug 'em," said Walt. "Go ahead," said Wes. "I'm utterly disgusted, though I think our trouble is due to the management of Terran Electric. They like legal tangles too much." "We'll give 'em a legal tangle," said Barney. He was adding circuits to the tablecloth sketch. * * * * * Channing, on his side, was sketching in some equations, and Walt was working out some mechanical details. Joe came over, looked at the tablecloth, and forthright went to the telephone and called Walton. The mechanical designer came, and Channing looked up in surprise. "Hi," he said. "I was about to call you." "Joe did." "O.K. Look, Ted, can you fake us up a gadget like this?" Walton looked the thing over. "Give me about ten hours," he said. "We've got a spare turnover driver from the _Relay Girl_ that we can hand-carve. There are a couple of water-boilers that we can strip, cut open, and make to serve as the top end. How're you hoping to maintain the vacuum?" "Yes," said Wes Farrell, "That's going to be the problem. If there's any adjusting of electrodes to do, this'll take months."