Voting method
The classes or types of machines used in a voting system. There are five types of voting methods used in U.S. elections: paper ballot, lever machine, punch card, optical scan, and DRE [Direct Recording Electronic (DRE) voting machine].
Source: ELECTIONS: The Nation’s Evolving Election System as Reflected in the November 2004 General Election, U.S. Government Accountability Office, https://www.gao.gov/assets/160/157713.pdf