<P> The first commercial voting systems to incorporate voter verified paper audit trail printers were the Avante Vote Trakker and a retrofit to the Sequoia AVC Edge called the VeriVote Printer . Avante's system saw its first trial use in 2002, and in 2003, the state of Nevada required the use of VVPAT technology statewide and adopted the Sequoia system . It is notable that, in Avante's design, the shield preventing the voter from taking the paper record was an afterthought, while in Sequoia's design, the paper record for successive voters were printed sequentially on a single roll of paper . </P> <P> Various technologies can be used to implement a paper audit trail . </P> <Ul> <Li> Attachment of a printer to direct - recording electronic (DRE) voting machines that print paper records stored within the machine . Such designs usually present the record to the voter behind a transparent surface to enable a voter to confirm a printed record matches the electronic ballot . The records can be manually counted and compared to the electronic vote totals in the event of a dispute . The solution linking electronic ballot images and the voter - verified paper record with randomly generated unique voting session identifier is covered by patents issued and pending . </Li> <Li> Attachment of a printer to DRE voting machines that print paper records on special paper with security features . The printed page contains both a plain text record and a simple barcode of the voter's selections . This page is the official ballot that is then fed through a scanner into a locked ballot box so that all originals are saved in case of the need for a recount or audit . The electronic record from the DRE is compared with the barcode scanner record and in case of any discrepancy, the paper ballots are used to determine the official vote, not the electronic record . The voter has the ability to proofread the ballot before it is placed into the scanner / lockbox and have it voided if there is any error, just as has always been possible with existing manual voting systems . </Li> <Li> Attachment of a printer to DRE voting machines that print an encrypted receipt that is either retained by the voter or stored within the machine . If the receipt is retained, the receipts can be manually counted and compared to the electronic vote totals in the event of a dispute . These systems have not been used in elections in the United States . </Li> <Li> Creation of an encrypted audit trail at the same time the electronic ballot is created in a DRE voting machine, a form of witness system . The audit trail can be accessed and compared to the electronic vote totals in the event of a dispute . </Li> <Li> Use of precinct - based optical scan or mark - sense tabulators instead of DREs . In this simple and cost - effective system, voters fill out paper ballots which are then counted electronically by a tabulator at the precinct, similar to the technology used to score standardized tests . Optical scan machines have been in use for decades, and provide a voter - verified audit trail by default . Tabulators can detect overvotes at the poll so that the voter can be given the opportunity to correct a spoiled ballot . </Li> </Ul> <Li> Attachment of a printer to direct - recording electronic (DRE) voting machines that print paper records stored within the machine . Such designs usually present the record to the voter behind a transparent surface to enable a voter to confirm a printed record matches the electronic ballot . The records can be manually counted and compared to the electronic vote totals in the event of a dispute . The solution linking electronic ballot images and the voter - verified paper record with randomly generated unique voting session identifier is covered by patents issued and pending . </Li>

Which are vvpat machines used for by the election commission of india