US Subs had their hydrophones, the round ones, mounted below the waterline so that when surfaced, they would still work. The JT listening gear available later in the war, mounted one on the port quarter foredeck, but they still had the older gear as a backup, and when in the middle of action, the secondary unit seved to keep the skipper informed of what was going on around them so that a DD couldn't as easily sneak up on them.
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A legislative act contrary to the Constitution is not law.
-John Marshall Chief Justice of the Supreme Court
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