Electronic voting in the United States involves several types of machines: touchscreens for voters to mark choices, scanners to read paper ballots, scanners to verify signatures on envelopes of absentee ballots, and web servers to display tallies to the public. Aside from voting, there are also computer systems to maintain voter registrations and display these electoral rolls to polling place staff. Most election offices handle thousands of ballots, with an average of 17 contests per ballot, so machine-counting can be faster and less expensive than hand-counting. Voluntary guidelines The Election Assistance Commission (EAC) is an independent agency of the United States government which developed the 2005 Voluntary Voting System Guidelines (VVSG). These guidelines address some of the security and accessibility needs of elections. The EAC also accredits three test laboratories which manufacturers hire to review their equipment. Based on reports from these laboratories the EAC certifies when voting equipment complies with the voluntary guidelines. Twelve states require EAC certification for machines used in their states. Seventeen states require testing by an EAC-accredited lab, but not certification. Nine states and DC require testing to federal standards, by any lab. Four other states refer to federal standards but make their own decisions. The remaining eight states do not refer to federal standards. Certification takes two years, costs a million dollars, and is needed again for any equipment update, so election machines are a difficult market. A revision to the guidelines, known as the VVSG 1.1, was prepared in 2009 and approved in 2015. Voting machine manufacturers can choose which guidelines they follow. A new version has been written known as the VVSG 2.0 or the VVSG Next Iteration, which is being reviewed. Optical scan counting In an optical scan voting system, each voter's choices are marked on one or more pieces of paper, which then go through a scanner. The scanner creates an electronic image of each ballot, interprets it, creates a tally for each candidate, and usually stores the image for later review. The voter may mark the paper directly, usually in a specific location for each candidate, then mail it or put it in a ballot box. Or the voter may select choices on an electronic screen, which then prints the chosen names, usually with a bar code or QR code summarizing all choices, on a sheet of paper to put in the scanner. This screen and printer is called