"turbo" wrote

OK it may be a dumb question, but I don't have an Oyster, but have seen
them
in operation a lot. Ok I put a £10 credit or whatever on this chipped card
and start using it- it doesn't have a display on it, neither does the
reader, how do I know the remaining credit... It just seems odd that I
could
have a valid oyster on the first part of my journey, which has 'expired'
by
the time I get on the bus to make the last part of a journey...

You can have a valid oyster when you touch in at the beginning of a tube
journey, but when you come to touch out several zones away you might not
have enough credit. Something similar can happen if you have an oyster
season, with no prepay, but go beyond your zone. AIUI the system can cope
with this, allowing the oyster to become overdrawn to a limited extent
(though I don't think it will allow you to start a journey if you are
overdrawn or have no credit)..

Peter