(65 ILCS 85/4) (from Ch. 111 2/3, par. 110.4)
    Sec. 4. Whenever refunding revenue bonds are issued under this Act, sufficient revenues received from the operation of such municipally owned utility shall be set aside as collected and be deposited in a separate fund which shall be used only in paying the cost of operation and maintenance of such utility and provide an adequate depreciation fund, and pay the principal of and interest upon the refunding revenue bonds issued under the provisions of this Act that are payable by their terms only from such revenues.
(Source: Laws 1941, vol. 1, p. 383.)