Ottens, who studied engineering, began working for Philips in 1952. By 1960 he had become head of the company’s product development department and within a year his team had developed the first portable tape recorder.
In 1963, Ottens revolutionized the reel-to-reel tape by inventing the cassette tape. Ottens later said the invention came about merely because he was annoyed with the “clunky, user-unfriendly reel-to-reel system.”
That same year the first cassette tape was introduced at an electronics fair with the slogan: “Smaller than a pack of cigarettes!”
Ottens later struck a deal with Sony to introduce a standardized design for the cassette tapes. More than 100 billion would be sold around the world over the proceeding decades.
In the 1970s, Ottens was instrumental in the development of what would eventually become the compact disc, or CD – something he believed held superior sound quality to cassettes.
Ottens retired in the late 1980s. He was always humble about his inventions, maintaining that they were team efforts, according to the Dutch paper NRC Handelsblad.