Roland Perry wrote:

Which implies that an almost unlimited amount of historic transaction
information is sent with every wave.

Not really, the retailer's POS system can do this with nothing more than
the card number.

Bus ticket inspections could be done by having the ticket machine print out
a ticket containing the last 4 digits of each credit card used during that
journey, perhaps. Or more technologically, communicate it to the
electronic gripping irons.

Neil
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Neil Williams in Milton Keynes, UK. Put first name before the at to reply.