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.

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