In a device equipped with an audio output, a range of the audio output
level in regular use is set. When an attempt is made to change the
setting to a volume level exceeding the range of the audio output level
having been set, a request is made for an acknowledgement that the
operation is appropriate, and only if a reply is received within a given
time, is the volume setting changed. Such a method prevents the audio
output from a television set or audio equipment to be increased to a
volume level higher than necessary due to an operating error in a volume
setting operation.