In 1866, at age 19, Edison moved to Louisville, Kentucky, working for The Associated Press. The night shift allowed him to spend most of his time reading and experimenting. He developed an unrestrictive style of thinking and inquiry, proving things to himself through objective examination and experimentation. Initially, Edison excelled at his telegraph job because early Morse code was inscribed on a piece of paper, so Edison's partial deafness was no handicap. However, as the technology advanced, receivers were increasingly equipped with a sounding key, enabling telegraphers to "read" message by the sound of the clicks. This left Edison disadvantaged, with fewer and fewer opportunities for employment.