Section 4535 - Audible warning devices(a) General rule.--Every motor vehicle operated on a highway shall be equipped with a horn or other audible warning device of a type approved in regulations of the department.(b) Certain sound devices prohibited.--Except as specifically provided in this part or by regulations of the department, no vehicle operated on a highway shall be equipped with a siren, bell, whistle or any device emitting a similar sound or any unreasonably loud or harsh sound.(c) Exceptions.--This section shall not apply to any special mobile equipment, commercial implement of husbandry or implement of husbandry that is not so equipped by the original manufacturer. 1976, June 17, P.L. 162, No. 81, § 1, effective 7/1/1977. Amended 1982, June 23, P.L. 605, No. 171, § 9, imd. effective; 1992, Dec. 18, P.L. 1411, No. 174, § 13, effective in 60 days.