if the Secretary determines that the order has been approved by a majority of manufacturers voting who also represent a majority of the machine cavities in operation of those manufacturers voting in the referendum. (b) Votes permitted (1) In general Each manufacturer eligible to vote in a referendum conducted under this section shall be entitled to cast one vote. (2) Eligibility For purposes of paragraph (1), a manufacturer shall be considered to be eligible to vote if the manufacturer has manufactured concrete masonry products during a period of at least 180 days prior to the first day of the period during which voting in the referendum will occur. (c) Manner of conducting referenda (1) In general Referenda conducted pursuant to this section shall be conducted in a manner determined by the Secretary. (2) Advance registration A manufacturer who chooses to vote in any referendum conducted under this section shall register with the Secretary prior to the voting period, after receiving notice from the Secretary concerning the referendum under paragraph (4) . (3) Voting The Secretary shall establish procedures for voting in any referendum conducted under this section. The ballots and other information or reports that reveal or tend to reveal the identity or vote of voters shall be strictly confidential. (4) Notice Not later than 30 days before a referendum is conducted under this section with respect to an order, the Secretary shall notify all manufacturers, in such a manner as determined by the Secretary, of the period during which voting in the referendum will occur. The notice shall explain any registration and voting procedures established under this subsection. (d) Subsequent referenda If an order is approved in a referendum conducted under subsection (a) , the Secretary shall conduct a subsequent referendum— (1) at the request of the Board, subject to the voting requirements of subsections (b) and (c), to ascertain whether eligible manufacturers favor suspension, termination, or continuance of the order