If it is learned by the radio inspector or any of his authorized deputies that any device, machine or apparatus coming within the provisions of this chapter is being operated in violation of the terms of this chapter, the radio inspector shall notify the city recorder, who shall promptly mail a notification to the owner, operator, or user of such device, addressed to the premises where the device is located, stating that the operation of such device during certain specified hours is in violation of this chapter and that the device must be repaired and equipped as required by this chapter, within three days, or its operation be discontinued during the specified hours. Mailing such a notification shall be sufficient for the purpose of this chapter.