Patent ID: 7599503

Claim:
A method of setting an audio output level comprising: storing a plurality of thresholds associated with clock time information preliminarily; selecting one of the plurality of thresholds corresponding to a current clock time; requesting an acknowledgement that a setting of the audio output level is to be changed, if the setting of the audio output level is to be changed to a setting that exceeds the selected threshold; allocating a function of replying to the acknowledgement to an operation button provided on at least one of a remote control unit and a main unit for a certain period of time immediately after requesting the acknowledgment; setting, in a setting unit, the audio output level to the setting that exceeds the selected threshold, if the reply via the operation button is received; and setting, in the setting unit, the audio output level to the selected threshold, if a reply via the operation button is not received by expiration of the certain time period.