The county commissioners, or such other authority as levies the taxes for county purposes of any county which adopts voting machines, or of any county in which a city, borough or township is located which adopts voting machines, shall, upon the purchase thereof, provide for payment therefor by the county: Provided, however, That bonds or other evidences of indebtedness, payable not later than thirty years from their dates of issuance, may be issued in accordance with the provisions of law relating to the increase of indebtedness of counties, to meet all or any part of the cost of the voting machines.