 In July 1911 three radio inspectors began working from the ports of New York City, San Francisco, and Baltimore.In response to the sinking of the RMS "Titanic" in April 1912, some of the provisions of the original act were strengthened by an amendment passed on July 23, 1912.Changes included adding vessels on the Great Lakes, requiring auxiliary electrical power supplies independent of a vessel's main power plant that were capable of enabling radio apparatus to be operated continuously for at least four hours at a minimum range of 100 miles (160 km), and a requirement that ships carry two or more operators and maintain a continuous watch.