Influence on electronic circuits, especially digital components 　 　 Traditional electrical appliances are not affected by tiny noise. For example, a light bulb for 100 V is still fine if an pulse of 1 V is superimposed. In the case of digital equipment, it is easily affected, resulting in an error. To reduce the noise emission and to protect the equipment from the noise are important to use the appliances safely. The difficult thing is such kinds of alliances become noise sources as well as being susceptible.