Complex sentence: He also paid close attention to his work quickly learning to distinguish the differing sounds the incoming telegraph signals produced and learned to translate signals by ear, without having to write them down and within a year was promoted as an operator.
Split into simpler sentences: He also paid close attention to his work, and quickly learned to distinguish the differing sounds the incoming telegraph signals produced. He developed the ability to translate signals by ear, without having to write them down, and within a year was promoted as an operator.