"They don't cost so much," said Alec. "It's the battery that's expensive."
"Tell me again what they were. Wait. Write it down."
Elsa brought a piece of paper and a pencil. Alec wrote down his list. Then he thought the matter over carefully. "Yes," he said, "those are all the pieces I need, though I ought to have a second set of receivers. They'd fix us up all right. If you get them, we can hear well, especially if the battery is freshly charged. We'll use them while I'm here, and after I go you can keep them as part of the set I'm going to make for you."
Elsa left the room. Presently Alec heard the purring of her motor-car. Then he sat in silence for a long time. Finally he heard a motor-car drive into the yard. Not long afterward Elsa came into the room, struggling with her Ford battery.
"Had it recharged," she panted, "and got all the things you wanted."
"Then we'll wire them right up," said Alec.
"I'm awful sorry, but I have to attend a rehearsal for our class play. I can't stay now."
Alec wired up the instruments himself. It was early evening, and atmospheric conditions seemed ideal for wireless communication.
"Now we'll see what the outfit will do," said Alec to himself, as he clamped a pair of receivers on his head and threw over his switch.
For a long time he listened and worked, tuning and adjusting his instruments. At first there was a frightful whistling and wailing in his ears. But gradually he tuned it out, eliminating all but the sounds he wished to hear.