Paul Corfield wrote:
On Fri, 25 Feb 2005 13:29:34 +0000, Dave Arquati wrote:


Ian Jelf wrote:

I took a trip on a 38 from Piccadilly to Victoria yesterday afternoon.

Unusually, the conductor worked like a Trojan during the trip, checking
fares, calling out stops (with a lot of additional information, too) as
well as warnings. It was a pleasure to see.

My query, though, concerns Oyster.

I paid by Oyster Prepay and at Victoria I left the bus and went straight
into the Underground Station to top up it up. When I did so, I was
astonished to see my journey on the 38 already recorded on my usage. How
does this data get from the conductor's machine to Oyster's "Central
Control" so quickly?

Aha... the conductor's machine doesn't actually hold your information.
The information is stored on the card itself, so when the conductor
marks a bus journey using his machine, that bus journey is stored on the
card. As soon as your card then comes into contact with the central
network (mainly via LU gates, ticket machines or validators) then that
information can be synchronised with the network.

At least that's how I understand it works.


Only partly correct I'm afraid.

The card will store 10 journeys worth of information. Therefore it is
updated each time there is a transaction such as an entry at a gate or
tapping your card on a bus reader. Both the card and reading device
exchange information and validity checks are made. There is a
transaction written to the card and also one generated in the reading /
checking device. As the conductor machine can deduct cash as well as
sell a paper ticket then it MUST record all transactions - how else is
the money accounted for?

I realise the conductor's machine must record the transactions, but the
station ticket machine also showed Ian's bus journey straight away. Does
it only read the information from the card, or does it also synchronise
with the central database - or is that left to the update from the
conductor's machine only?

I also presume some new software had to be downloaded into every single
Oyster reader for the introduction of capping - I wonder whether this
has been done in advance with it only becoming "switched on" tomorrow?

(snip some very useful detail)

--
Dave Arquati
Imperial College, SW7
www.alwaystouchout.com - Transport projects in London