In addition to the codes adopted by this chapter by reference, it shall, in addition, be unlawful within the city for any person to operate brakes upon a motor vehicle which are in any way activated or operated by the compression of the engine of any such motor vehicle or any unit or part thereof. Provided, however, that it shall be a defense to such a violation if said compression brakes were applied in an emergency and were necessary for the protection of persons and/or property. Provided, further, that this section shall not apply to the operation of emergency equipment by public fire personnel operating emergency equipment within the city nor to persons operating vehicles for public conveyance within the city. (Ord. 913 §2, 1991).