Any securities issued by the corporation may from time to time thereafter be refunded by the issuance of refunding securities of the corporation, but the amount of any refunding securities so issued shall not exceed the principal of the securities refunded thereby together with any unpaid interest thereon, any redemption premium thereon and any expenses of such refunding. Any such refunding securities may be issued regardless of whether the securities to be refunded shall have then matured or shall thereafter mature, and such refunding may be effected either by sale of the refunding securities and the application of the proceeds thereof to the payment or redemption of the securities so refunded or by exchange of the refunding securities for those to be refunded thereby; provided, that the holders of any securities so to be refunded shall not be compelled without their consent to surrender their securities for payment or exchange prior to the date on which they are payable or, if they are called for redemption, prior to the date on which they may be redeemed by the corporation according to their terms. Any refunding securities of the corporation shall be payable solely from and secured by the revenues out of which the securities to be refunded thereby were payable. The proceeds derived from any sale of refunding securities shall be applied to the purchase, redemption or payment of the securities refunded thereby. Pending the application of said proceeds to the purchase, redemption or payment of such outstanding securities, the said proceeds may be invested in eligible investments pursuant to an escrow or trust agreement providing for the future application of such proceeds to the purchase, redemption or payment of such outstanding securities.