"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."