"That's the point. I think he _can_ hear it. He can't _recognize_ it, but that isn't quite the same thing. His eardrums still vibrate, the data gets in, all right. But it doesn't reach the conscious level. Fortunately, it isn't always necessary to be consciously aware of a stimulus before you can respond to it. Frequently a persistent stimulation just below the threshold of awareness will produce a response in the organism. Sub-threshold stimulation, it's called." "Yeah," Banning said, "I've heard of it. Used it in advertising, didn't they?" "For a while. Before Congress passed the Privacy Amendment." "Okay. Now what?" "Now we wait and see if it works. I'm going to take a nap. Wake me up if anything happens." Colin stretched out on one of the cots, put his hands behind his head and soon was breathing deeply in an excellent imitation of sleep. * * * * * The clock on Banning's desk said 4:33 when his communicator chimed. Banning was off his cot and at the desk before the first soft echoes faded. "Banning. Yes ... yes ... all right, right away." "What is it?" Colin asked. "They've got something from the _Phoenix_ at Control." When they reached the radio room again, a different technician was on shift. He was intently watching an oscilloscope face on the board in front of him. "What happened, did he answer?" the general asked. "No, sir. But a few minutes ago we started getting a carrier wave on his transmission frequency." Banning sighed disgustedly. "Is that all? Dammit!" "What does that mean?" Colin asked. "Not a damned thing," Banning said angrily. "He just threw the transmission switch, is all." "Look, sir." The radioman pointed to the oscilloscope. The smooth sine of the carrier was slightly modulated now, uneven dips and jogs appearing rhythmically. "There's something coming through, but it's awfully damned faint, Sir." "Run your sensitivity up," Banning ordered. The radioman slowly twisted a knob, and the hiss-and-crackle coming through the speakers increased in volume until each snap was like a gunshot in the radio room. Colin winced at the noise. "Maximum, sir." "Increase your gain, then." The technician did. The speakers were roaring now, filling the room. Very faintly behind the torrent of sound another sound could be heard, more regular. The rhythm corresponded with the jogging of the oscilloscope. "That's it," Banning said. "But what the hell is it?" "I don't--wait a minute," said Colin. "He's whistling! It's a tune." "You recognize it?" "No--no, it's vaguely familiar, but--" "I know it, sir," the radioman said. "It's an old folksong, _The Quaker's Wooing_." "Why is it so faint?" asked Colin. "He must be a hell of a ways off-mike," said the tech. "Clear at the other end of the control room, I'd say." "Turn down that damned noise," said Banning. The radioman twisted his controls back to medium range, and the thunderous hissing roar of the speakers died away.