Farrell was working furiously on the detector device, and as they entered, he indicated the meter that was jumping up and down. Out of a speaker there was coming the full, rich tones of Freddy Thomas' voice, announcing solemnly: "One, two, three, four, test."
Wes said: "I'm getting better. Charley has been bettering his modulator now, and the detector is three notches closer to whatever this level of energy uses for resonance. Evacuation and the subsequent incandescence was the answer. Another thing I've found is this—" Farrell held up a flat disk about six inches in diameter with a sawcut from edge to center. "As you see, the color of this disk changes from this edge of the cut, varying all the way around the disk to the other side of the cut. The darned disk is a varying alloy—I've discovered how to tune the driver radiation through a limited range. We hit resonance of the Relay Girl's driver system just off the end of this disk. But watch while I turn the one in the set."
Farrell took a large knob and turned it. Freddy's voice faded, and became toneless. Farrell returned the knob to its original position and the reception cleared again. "Inside of that tube there," said Farrell, "I have a selsyn turning the disk, and a small induction loop that heats the whole disk to incandescence. A brush makes contact with the edge of the disk and the axle makes the center connection. Apparently this stuff passes on a direct line right through the metal, for it works."
"Have you tried any kind of tube amplification?" asked Don.
"Not yet. Shall we?"
"Why not? I can still think that the relay tube will amplify if we hook up the input and output loads correctly."
"I've got a tube already hooked up," said Walt. "It's mounted in a panel with the proper voltage supplies and so on. If your resistance calculation is correct, we should get about three thousand voltage gain out of it."
He left, and returned in a few minutes with the tube. They busied themselves with the connections, and then Don applied the power.
Nothing happened.