The metallic, monotonous voice came from that audio-speaker. It was still speaking steadily on, and everything it said was being taken down upon the moving tape of a recorder whose microphone hung in front of the speaker.
"Think of something else,” the metallic voice came from the speaker as the Planeteers listened. “Think of the Zone — of Stilicho — of my father—"
"A psychophone!” repeated Sual Av, wide-eyed. “So that's how Trask is trying to get the secret of Erebus from Lana!"
Thorn too was thunderstruck by the ingenuity of the means being used to secure the girl's secret knowledge.
The psychophone was a mechanism that made thought audible. Once it was connected to a subject's nerve centers, every conscious thought in that subject's brain was translated into mechanical speech by the machine and spoken aloud. That was accomplished by transmitting the tiny electrical neural currents of the subject's thought-impulses into a complex scanner, in which the particular vibration of each thought actuated the nearest word or phrase that expressed that thought, in the phono-recorded vocabulary of the thing.
The machine was the recent and little-known invention of a Venusian psychologist. It was a far-advanced adaptation of the ancient encephalograph, the device used by Earth scientists as far back as the third decade of the twentieth century to record thought as a varying electrical vibration.
Lana Cain was sitting silent, her eyes closed, but every thought that passed through her mind was being remorselessly translated and spoken aloud by the mechanism above her head, and taken down by the recorder so that it could be studied later at leisure. She could not possibly keep from thinking, and whatever she thought, the psychophone spoke forth.
"M-my father,” the mechanical voice was speaking on as Thorn and his comrades peered incredulously."Wish my father were alive. He would get me out of here. He would—"
"Lana!” Thorn whispered tensely into the cell.
The girl opened her eyes. Their blue depths were wells of utter weariness and hopelessness as she stared at Thorn's face through the grating in the door.