N.J. Stat. § 40:3-10
Investment of sinking fund moneys shall be restricted to unlimited obligations issued by the United States of America, or bonds of the State of New Jersey, or bonds of any county, school district or municipality of this State, or the negotiable notes of any county, municipality or school district of this State, but except as herein otherwise provided the date of maturity of such investments shall be such that with subsequent accretions to the fund there shall be moneys on hand to pay the several issues of bonds as they fall due.
If in the judgment of the majority of the sinking fund commissioners it is inexpedient and not to the best interests of the sinking fund to sell such securities held in the fund, the commission may borrow funds to meet maturing bonds, using as collateral for such loans any of the securities held in the fund.
N.J.S. § 40:3-10