It shall be unlawful for any person, knowingly or wantonly, to operate or cause to be operated any machine, device, apparatus or instrument of any kind whatever within the city, the operation of which shall cause reasonably preventable electrical interference with radio or television reception within the city; provided, that X-ray pictures, examinations or treatments may be made at any time and violet ray machines, machines using the Telsa coil or principle, diathermic machines and other machines of like character may be used at any time if the machines or apparatus are properly equipped to avoid all unnecessary or reasonably preventable interference with radio or television reception and are not negligently operated. (Code 1953, § 12.31)