This line fostered a fundamental change in music listening habits by allowing people to carry music with them and listen to music through lightweight headphones.[1][75] Originally used to refer portable audio cassette players, the Walkman brand has been widely adopted by the company to encompass its portable digital audio and video players as well as a line of former Sony Ericsson mobile phones. In the case of optical disc players, the Discman brand was used until the late 1990s. In 1999 Sony's first portable digital audio players were introduced; one was a player using Memory Stick flash storage created by the Walkman division, and the other was a smaller pen-sized player with embedded flash storage created by the Vaio division; both accompanied with Sony's OpenMG copyright protection technology and PC software for music transfer.[76][77]