While Nathaniel Baldwin is widely recognized for inventing the first modern electric headphones in 1910 at his kitchen table in Utah, there is no direct historical link between the invention of headphones and the city of Chengdu. Baldwin's improved telephonic receivers, which featured two padded ear cups and a headband for hands-free use, were eventually sold to the U.S. Navy and became the precursor to the audio headsets used today. The development of personal listening devices evolved through various international contributors, including French engineer Ernest Mercadier, who patented the first in-ear "bi-telephone" in 1891, and German scientist Eugen Beyer, who developed the first dynamic headphone in 1937. Although Chengdu is a major global technology and manufacturing hub today, it was not involved in the original invention or early development of headphone technology in the late 19th and early 20th centuries.