Ala. Code § 11-50A-19
All or any part of the gross or net revenues derived from any particular project or projects, whether or not such revenues were produced by a particular project for which bonds have been issued, and any income and earnings otherwise received by the authority from whatever source, and any other funds of the authority, may be pledged by the authority to the payment of the principal of and interest on bonds as may be provided in any resolution authorizing the issuance of any bonds or in any trust agreement or indenture pertaining to those bonds. The funds so pledged may include funds received from one or more or all sources and may be set aside at regular intervals into sinking funds for which provision may be made in any resolution, trust agreement or indenture pertaining to the bonds. These sinking funds may be pledged to and charged with the payment of (i) the interest on the bonds as it shall become due, (ii) the principal of the bonds as they shall mature, or as they are required to be redeemed, (iii) the necessary charges of any trustee or paying agent or registrar for the bonds, and (iv) any premium upon bonds retired upon call or purchase, and the use and disposition of any sinking fund may be subject to regulations for which provision may be made in the resolution, trust agreement or indenture pertaining to the bonds.
Ala. Code § 11-50A-19 (1975)