(a) Authority bonds issued may be secured by a pledge of all or part of the authority's revenue or by all or part of the revenue of one or more contracts made or other revenue or income specified by board resolution or a trust indenture securing the bonds. The pledge may reserve the right, under conditions specified by the pledge, to issue additional bonds that will be on a parity with or subordinate to the bonds then being issued.
(b) The authority may issue bonds secured by both taxes and revenue of the authority described by Subsection (a).