Green light card dating
The readers read information from the cards, calculate whether to allow travel, assess any fare payable and write back information to the card.
Some basic information about the MIFARE Classic or MIFARE DESFire chip can be read by any ISO/IEC 14443 type A compatible reader, but Oyster-specific information cannot be read without access to the encryption used for the Oyster system.
They are activated only when they are in an electromagnetic field compatible with ISO/IEC 14443 type A, provided by Oyster readers.
The card is designed to reduce the number of transactions at ticket offices and the number of paper tickets.
Usage is encouraged by offering substantially cheaper fares than with cash with a limited range of features and there continues to be a phased introduction of further functions.
By June 2012, over 43 million Oyster cards had been issued and more than 80% of all journeys on public transport in London were made using the card.
The Oyster card was set up under a Private Finance Initiative (PFI) contract between Transport for London (Tf L) and Tran Sys, a consortium of suppliers that included EDS and Cubic Transportation Systems (responsible for day-to-day management) and Fujitsu and WS Atkins (shareholders with no active involvement).