Radio Shack 120-0914 - Manual (Page 4)

Once you set the volume, do not increase it. Over time, your ears adapt
to the volume level, so a volume level that does not cause discomfort
might still damage your hearing.
Traffic Safety
Do not wear headphones while operating a motor vehicle or riding a bicycle.
This can create a traffic hazard and is illegal in some areas.
Even though some headphones are designed to let you hear some outside
sounds when listening at normal volume levels, they still present a traffic
hazard.