(a) A voting machine to be used in Tennessee must provide facilities for voting for candidates at both primary and general elections, at nonpartisan elections or at a combination of a nonpartisan and partisan primary or general election. It must permit a voter to vote for any person for any office, whether or not nominated as a candidate by a political party. It must ensure voting in absolute secrecy. It must permit a voter to vote for any candidate or on any special measure for whom or on which the voter is lawfully entitled to vote but none other. It must permit a voter to vote for the proper number of candidates for an office but no more. It must be provided with a lock or locks by which immediately after the polls are closed any movement of the voting or registering mechanism can be absolutely prevented. It may be either manually or electrically operated. An electric machine must convert to manual operation, and the alternate type of operation must be a standard function of the machine and not be designed as an emergency or temporary device only. Each voting machine shall have not less than eight (8) columns and shall be equipped with interlocks in the following manner:

(1) for the basic lever type machine, interlocks on columns 1, 4, and 7;

(2) for the 2.5 lever type machine, interlocks on columns 1, 4, and 7 and an additional main interlock adjacent to column 10;

(3) on the 3.2 eight column machine, interlocks on columns 1, 4, and 7 and an additional main interlock adjacent to column 8; and

(4) on the 3.2-10.25 lever type machine, interlocks on columns 1, 4, and 7 and an additional main interlock adjacent to column 10.

(b) Any voting machine not presently equipped as described in (a) shall be modified pursuant to a contract to be let by the coordinator of elections through normal purchasing procedures. The contract shall contain such provisions as the coordinator of elections, secretary of state and commissioner of finance and administration shall deem necessary and proper, and shall provide for the use of new parts only. Furthermore, the contract shall provide for the inspection of parts, labor, and equipment by a team of local machine technicians, and the costs of such inspection at the local level shall be borne by the company or firm awarded the contract.

(c) A party lever device enabling a voter to vote for all the nominees of a particular political party by operating a single lever is prohibited except that a party lever shall be provided for each political party's candidates for presidential and vice presidential electors.