0 a small electronic device that plays music and has headphones so that you can listen to music while you are doing other things
I thought that he might have nodded off and that perhaps the headphones were his personal stereo.
I should also like to recommend that the habit of cycling while wearing and listening to personal stereo systems should become an offence.
However, quarter-inch phone connectors are still common in professional audio, and miniature phone connectors (3.5 mm) are predominant in personal stereo systems.
Personal stereo sets are not capable of generating very high volumes, although the use of earphones means that lower volumes are more concentrated.