How the Electronic Voter Machines work:
1) Candidates' names are written in the majority languages and scripts of the constituency. To help illiterate voters, each candidate is also identified by a symbol: the lotus for the BJP, for example, or a hand for Congress. Non-affiliated candidates can choose a symbol from an approved list.
2) Voters press the blue button next to their preferred candidate to cast their ballot. For the first time, there is a button for None of the Above, as well as a serial number in Braille to help visually impaired voters.
3) The control unit stores the votes and runs on a battery so that it can keep working in case of a power cut. During counting, the serial number of each candidate appears, along with the total number of votes cast.
Once poll officials press the Close button under the flap, the machine stops recording any more votes. It is used at the end of polling or if anybody tries to forcibly enter a polling station with the intention of casting fraudulent votes.
4) To prevent anyone tampering with the unit holding the voting information, the unit is sealed with old-fashioned wax, supplemented by a secure strip from the election commission and a serial number.
Text and picture from BBC.
(From the archive: The Explainer: What is Fiscal Deficit?)