In the case of older mechanical voting machines, when a voter enters the booth and closes the curtain by means of a lever, the machine unlocks for voting. The titles of all elective offices are listed on the face of the machine along with the party candidates running for each office. Above each name is a lever which, when depressed, indicates a vote for that candidate. Only one candidate for each office may be selected. Write-in votes are possible and propositions are placed at the top of the ballot. When the voter pulls the curtain open to leave, the machine automatically registers the vote and is cleared for use by the next person.
The mecahnical voting machine was first used in New York state in 1892, and came to be used throughout the United States. Faster and more accurate in tabulating the vote than the paper ballot, mechanical voting machines were gradually replaced in many parts of the United States in the late 20th cent. by so-called electronic or computerized voting machines. In one form of electronic voting, voters indicate their preferences using punch cards that are read by computer, but in the United States punch cards fell out of favor after their use led to controversy in the 2000 presidential election. Both lever-type mechanical voting machines and punch-card-based machines were replaced by other systems with federal aid provided under the Help American Vote Act (2002).
Other modern voting technologies include the optical-scan system, in which marked ballots are read by computer using optical sensing, and the direct-record electronic voting system, in which a voter chooses a candidate by means of push buttons or touch screens on a computerized voting machine, which tallies the votes. A number of experts, including the National Institute of Standards and Technology, have called for direct-record electronic systems to have increased safeguards against potential computer tampering and/or to provide a paper record of an individual's vote so that a non-electronic means of recounting a challenged electoral result would exist.
Estonia has used Internet voting, via a website, as an alternative form of voting. Voters use a computer-readable identification card and enter two passwords before they vote. The method was pioneered in local elections in 2005 and used in national elections in 2007.
The voting machine's greatest asset is protection against voting fraud or human error. However, critics claim that it intimidates some citizens, that some machines are subject to breakdown, and that fraud is not completely eliminated. Computerized voting machines that use punch cards are also susceptible to voter error, as they lack the means to prevent a person from voting for two candidates for the same office, and can fail to register a vote clearly.
For many years the United States was the only country that used voting machines extensively; Brazil now uses a national computerized voting system. The cost of voting machines, combined with less frequent elections and simpler ballots in many countries, make them impractical for worldwide use.
A voting system includes the practices and associated documentation used to identify system components and versions of such components; to test the system during its development and maintenance; to maintain records of system errors or defects; to determine specific changes made after initial certification; and to make available any materials to the voter (such as notices, instructions, forms, or paper ballots).
Traditionally, a voting machine has been defined by the mechanism the system uses to cast votes and further categorized by the location where the system tabulates the votes.
Voting machines have different usability, security, efficiency and accuracy. Certain systems may be more or less accessible to all voters, or not accessible to those voters with certain types of disabilities. They can also have an effect on the public's ability to oversee elections.
Punchcard systems employ a card (or cards) and a small clipboard-sized device for recording votes. Voters punch holes in the cards (with a supplied punch device) opposite their candidate or ballot issue choice. After voting, the voter may place the ballot in a ballot box, or the ballot may be fed into a computer vote tabulating device at the precinct.
In the 1996 Presidential election, some variation of the punchcard system was used by 37.3% of registered voters in the United States.