Abstract

A CPU is designed so as to put a demagnetizing circuit in an operative state in accordance with a result of detecting, among other quantities or events, the number of operations to turn on a power counted by a counter, the lapse of time under a predetermined condition measured by a timer since the pulling-out of an AC plug, the movement of the main body of a display device sensed by a sensor unit, an external magnetic field sensed by a sensor unit or a residual magnetism in a CRT itself sensed by a sensor unit. Instead of carrying out demagnetization each time the power is turned on, demagnetization is performed only under certain conditions when necessary, diminishing the problem of wasteful power consumption. On the top of that, the number of cases in which sound and picture vibration are generated due to a demagnetizing operation carried out right after the turning-on of the power is reduced, resulting in a product easy to handle by the user. In addition, the lives of components composing a demagnetizing circuit such as a positive thermistor can be prolonged.