an electronic ballot marker (EBM) or ballot marking device (BMD), and voters with disabilities can communicate with it by headphones, large buttons, sip and puff, or paddles, if they cannot interact with the screen or paper directly. Typically the ballot marking device does not store or tally votes. The paper it prints is the official ballot, put into a scanning system which counts the barcodes, or the printed names can be hand-counted, as a check on the machines. Most voters do not look at the machine-printed paper to ensure it reflects their choices. When there is a mistake, an experiment found that 81% of registered voters do not report errors to poll workers. No state requires central reporting of errors reported by voters, so the occasional report cannot lead to software correction. Hand-marked paper ballots more clearly have been reviewed by voters, but some places allow correction fluid and tape so ballots can be changed later. Two companies, Hart and Clear Ballot, have scanners which count the printed names, which voters had a chance to check, rather than bar codes and QR codes, which voters are unable to check. When scanners use the bar code or QR code, the candidates are represented in the bar code or QR code as numbers, and the scanner counts those codes, not the names. If a bug or hack makes the numbering system in the ballot marking device different from the numbering system in the scanner, votes will be tallied for the wrong candidates. This numbering mismatch has appeared with direct recording electronic machines (below). Errors in ballot marking devices Ballot marking devices display contests and candidates on a screen where voters can make, change and check selections before printing the choices on paper to put in a ballot box. The election worker provides a code for each voter, to tell the machine what contests that voter may vote on. Contests presented to voters depend on the district boundaries they live in. in a 2022 election in Marietta, GA, up to 157 voters were presented lists of contests which were partly in error, due to recent changes in district boundaries. Errors in optical scans Scanners have a row of photo-sensors which the paper passes by, and they record light and dark pixels from the ballot. A black streak results when a scratch or paper dust causes a sensor to record black continuously. A white