To illustrate Joe made the dot-dash sign, at which Hank blinked his eyes, but resolutely suppressed other symptoms of nervousness.
“And so on through the alphabet. Each letter has its own combination of dots and dashes. The only instruments needed in a simple set are the coil, spark-gap, wireless key and batteries; that is, for a sending set. Now we come to the receiving part of it.
“Suppose another operator miles away has been sending out into space the dot-dash just as I have been doing. If I had my receivers on, that is, those telephone-like things that I put on my head and over my ears, why then I’d have heard it, providing my apparatus was tuned to his wave lengths.”
“Hold hard! Hold hard! I don’t quite get that.”
“Simple enough. As I told you, various shocks of current produce various wave lengths. Well, suppose my receiving apparatus is only adjusted to receive a wave length of one thousand feet, and he is sending a wave of one thousand two hundred feet, then my apparatus will not be ‘in tune’ with his. That is, I shouldn’t be able to hear him.”
“Wa’al, how d’ye fix that—by touching off them biting things?” asked Hank. “Look a’out!” he added, as he saw Joe’s hand move toward the receiving tuning coil, “you ought’er have them things muzzled. If they bit you in the dog-days you’d git hydrophoby, sure as cock-fightin’.”
“Now then, Hank, a receiving tuning coil is used to adjust the wave lengths of the receiving circuits. This tuning, as it is called, is very simple. See, I move these sliding contacts along a bar, at the same time listening in. As soon as I am ‘in tune,’ I hear the dots and dashes from the other chap begin beating into my ears. Easy, isn’t it?”
“Humph, ’bout as easy as walkin’ a tight rope or running an air-ship! Joe, I couldn’t larn nothun’ ’bout such didoes in a billion, trillion of years.”
“In order to get the waves from the aerials into the receivers at my ears, they have to filter through the detector——”
“That’s the thing that bit me, that d’tector.”