The 3.5mm headphone jack is a dying breed - most smartphone manufacturers are skipping it, especially on higher-end devices. But its story deserves to be told, the jack has been around almost as long as phones, its original use was in 19th century switchboards when human operators manually connected your call. They needed a way to easily make and break electrical connection that carry audio. Today's use of the jack is much the same, even if most audio lives in the digital domain (of course, it's inevitably transformed into an analog signal before it can reach your ears). Phone jacks...
Source: https://www.gsmarena.com/flashback_the_headphone_jack_has_been_around_for_over_100_years_still_has_a_place_on_phones-news-41946.php
