Patent ID: 8558717

Claim:
A method of notifying an alert status, comprising: indicating alert status information using an alert status indication field that comprises at least two binary bits; changing a value of the alert status indication field to one of three or more different values when the alert status information is changed; periodically sending the alert status information when the value of the alert status indication field is changed, judging whether an alert occurs by a second judging unit; setting at least one binary bit that indicates whether the alert occurs or not in the alert status indication field to a second value when no alert occurs and setting the at least one binary bit that indicates whether the alert occurs in the alert status indication field to a third value when the alert occurs by a second setting unit; judging whether the alert status information is changed by a third judging unit; and changing a value of at least one other binary bit that indicates the change to the alert status information based on a judgment result of the third judging unit when the alert status information is changed by a third setting unit.