S. 6412, An Act to regulate radio communication (Radio Act of 1912), May 20, 1912
Following the Titanic investigation, which found that radio interference contributed to delays in rescue operations, Congress began regulating transmissions with the Radio Act of 1912 and amendments to the Wireless Ship Act of 1910. The Radio Act of 1912 required all radio operators to be federally licensed and all ships to maintain constant radio alert for distress signals.
Records of the U.S. House of Representatives, National Archives and Records Administration

The Sinking of the RMS Titanic
On April 14, 1912, the British ship Titanic collided with an iceberg and sank. More than 1,500 of those aboard died, including scores of Americans. To understand the cause of the accident, a Senate Committee on Commerce subcommittee acted quickly to obtain testimony from survivors, witnesses, rescuers, and officials. The subcommittee concluded that the catastrophe was an “act of God,” but criticized certain actions of the Titanic’s builders, owners, and crew. Congress responded with the Radio Act of 1912 and other legislation to improve maritime safety.
Our course was simple and plain—to gather the facts relating to this disaster while they were still vivid realities. . . . It was vital that the entire matter should be reviewed before an American tribunal if legislative action was to be taken for future guidance on international maritime safety.
Senator William A. Smith of Michigan, Speech to the Senate, May 28, 1912