Charles Adler Jr. was an inventor and engineer born in 1899 in Baltimore, Maryland. He attended John Hopkins University and briefly joined the army. Later he joined the Maryland and Pennsylvania Railroad developing safety devices. In 1928 he designed the first audible traffic horn. He was granted over 60 patents in his lifetime, 10 of which he donated to the government. He was a member of the Maryland State Aviation Commission and the Maryland Traffic Safety Commission.
From the guide to the Charles Adler, Jr., Papers, 1946-1952, (New York University Archives)