A. The emission of sound for the purpose of alerting persons to the existence of an emergency or the emission of sound in the performance of emergency works for as long a period of time as is necessary to constitute adequate alerting of persons to the existence of the emergency or the emergency work;

B. Warning devices for the protection of the public safety, as for example, police, fire, ambulance, commercial, residential and vehicle alarm devices, and train horns;

C. All mechanical devices, apparatus or equipment which are utilized for the protection or salvage of agricultural crops during periods of potential or actual frost damage or other adverse weather conditions. (Ord. 3924 § 3, 1999)