Complex sentence: Walkman is a Sony brand tradename originally used for portable audio cassette players in the late 1970s, and in the 2010s, it is used to market Sony's portable audio and video players as well as a line of former Sony Ericsson mobile phones.
Split into simpler sentences: Walkman is a Sony brand tradename originally used for portable audio cassette players in the late 1970s. In the 2010s, it is used to market Sony's portable audio and video players as well as a line of former Sony Ericsson mobile phones.