"Only," grunted the sergeant, "it ain't frequency we got to figure, but type. Nobody hardly uses anything but sine waves for communication, but I got to make this gadget turn out a freak wave-type by guess and golly. I got a sort of test for it, though."
He straightened up and connected a cable from the generator to the Mark IV communicator which was a factory twin of Betsy.
"I'm gonna feed this communicator half a micro-micro-watt of stuff like the broadcast—I think," he announced grimly. "I saw the diagrams of the transmitters they want us to make. I'm guessing the broadcast-wave they use is close to it but not exact. Close, because it's bad for machines. Not exact, because they're alive while they use it. I hope I don't hit anything on the nose. Okay?"
Lecky said gently:
"I have never been more frightened. Go ahead!"
Sergeant Bellews depressed a stud. The communicator's screen lighted up instantly. It was receiving the generator's minute output and accepted it as a broadcast. But the signal was unmodulated, so there was no image nor any sound.
The communicator's standby light flickered steadily.
Sergeant Bellews adjusted a knob on the generator. The communicator's standby flicker changed in amplitude. Bellews turned the knob back. He adjusted another control. The standby light wavered crazily.