Ed. Code, § 15230

The board of supervisors by an order entered upon its minutes shall fix the time when the whole or any part of the principal of the bonds shall be payable, which shall not be more than 25 years from the date of the bonds. If the governing board of the district has prescribed in its resolution the time or times when the whole or any part of the bonds shall be payable, the times and amounts shall be fixed by the order of the board of supervisors.

Any bonds authorized at an election held after September 15, 1945, may be issued subject to call and redemption before maturity at the option of the governing board of the district. The governing board may include in its resolution a requirement that all or any part of such bonds shall be issued subject to call and redemption before maturity and the price or prices at which the bonds shall be redeemed. The board of supervisors, in its order fixing the form of the bonds and the maturities thereof, shall provide that the bonds be redeemable at the option of the governing board and at the price or prices fixed in the resolution. Bonds issued subject to call and redemption prior to maturity shall contain a recital to that effect, and no bond shall be subject to call or redemption prior to maturity unless it contains that recital. The board of supervisors in its order shall fix the method of giving notice of redemption to holders of bonds to be redeemed.