On Tue, 08 Jun 2010 22:10:25 +0100, "
wrote:

How is information from an Oyster card relayed when you tap in on a bus?
If you are on pay as you go, for example, and change busses, then the
indicator on the second bus already shows that previous fare was
deducted from the first bus.

When a valid transaction is made the relevant info is updated on the
card itself and also recorded in the bus ticket machine (or validator or
ticket gate on rail or tram systems). The collected data is sent to the
central system for accounting, usage and card transaction history
purposes on rail and tram networks. For buses it is collected from the
driver module when the driver completes his shift and signs off at the
garage.

The next time you use the card it is read by the next Oyster enabled
device and depending on the rules you may or may not need to pay extra
(e.g. in zone or you've reached your daily cap). None of this is
particularly difficult.

There is not any real time Oyster data transmission from buses to the
centre or bus to bus. Obviously buses are in contact with the network
control via radio and for I-Bus service management but I don't believe
the system has sufficient capacity to provide secure financial
transaction data transmission.
--
Paul C