The duplicate registration record cards shall remain permanently in the office of the Board of Election Commissioners; shall be filed alphabetically without regard to wards or precincts; and shall be known as the master file. The master file may be kept in a computer-based voter registration file or paper format, provided a secondary digital back-up is kept off site. The digital file shall be searchable and remain current with all registration activity conducted by the Board of Election Commissioners. The original registration record cards shall constitute the official precinct registry of voters; shall be filed by wards and precincts; and shall be known as the precinct file. The original cards shall be delivered to the judges of election by the Board of Election Commissioners in a suitable binder or other device, which shall be locked and sealed in accordance with directions to be given by the Board of Election Commissioners and shall also be suitably indexed for convenient use by the precinct officers. The precinct files shall be delivered to the precinct officers for use at the polls, on the day of election and shall be returned to the Board of Election Commissioners immediately after the close of the polls. The board shall determine by rules the manner of delivery and return to such file. At all other times the precinct file shall be retained at the office of the Board of Election Commissioners except for such use of it as may be made under this Article with respect to registration not at the office of the Board of Election Commissioners.