Tom frowned, trying to get his train of thought to focus once more on
the submarine problem. But for some reason the business with the
microphone and the speaker in the next room kept lingering in his mind.
Suddenly Tom exclaimed aloud, "Say! I wonder if that's how the enemy sub
blinds our sonar?"
The idea certainly seemed feasible. Suppose the submarine used a great
many "microphones"--or receiving transducers--to pick up the sonar
pulses beamed out by another craft trying to detect it? These impulses
could then be passed on and sent out by speakers on the opposite side of
the sub, and relayed along on their underwater path of travel.
Thus the sonar waves would appear to be striking no obstacle--and no
echo would return to the sonarscopes on the search craft!
"Jumping jets!" Tom thumped his fist on the workbench in his excitement.
"I'll bet that's the answer, all right!" He grinned. "Brand my boot
heels, it's partly due to good old Chow!"
He grabbed a pencil and began sketching his idea on paper. It would be
necessary to spot the receivers and transmitters all over the hull of
the submarine. Diagrams and pages of scribbled computations followed the
rough sketches.
An invisible sub--one that sonar pulses would seem to pass right
through, as if nothing were there! "Seems so simple now that I have the
key!" Tom said to himself elatedly.
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