Fla. Stat. § 132.15

If the refunding bonds bear a lower rate of interest than the bonds for which they are exchanged, either the resolution authorizing the bonds or the refunding bonds themselves may provide that the refunding bonds shall bear the lower rate of interest only so long as the unit shall not be in default of any agreement or obligations to the holders and that after any such default, or at the option of the holders after any such default, the refunding bonds shall bear the same rate of interest as the bonds for which they were exchanged. The unit may impose limitations on the right to exercise such option, and may provide that the option may only be exercised after a period of default, or by the holders of a certain amount or proportion of bonds, all as provided in the said resolution or in the refunding bonds, and if the right to the higher interest accrues may agree to substitute new bonds and coupons bearing such higher interest.