ORS § 370.150
After the issuance of bonds has been authorized by an election held in accordance with ORS 370.031, 370.120 and 370.130, the county court, in lieu of bonds redeemable only at the time stated in the notice, may issue bonds and, in the order providing for their issuance, reserve the right to redeem any or all of them serially each year. When bonds are issued with such reservation, the redemption fund provided for in ORS 370.170 may be used each year, as it is collected, for the redemption of such proportion or percentage of the bonds as will redeem all of them at the end of the time fixed in the prior proceedings for maturity of the bonds, instead of being kept and deposited as provided by law or loaned as provided in ORS 370.200 until the final maturity of the bonds.
ORS 370.150