On 21/03/2012 06:56, Roland Perry wrote:

In message , at 06:43:49 on
Wed, 21 Mar 2012, Charles Ellson remarked:

What we haven't yet uncovered is what the equivalent mechanism is for
the under-18's VISA Debit cards which have replaced them.

...

I do have a sneaking suspicion that to some extent it might work by
making kids believe their cards can't go into the red but without any
certain method of enforcing that while the card is used away from any
communication with the bank.

At least one bank *promises* them they can't. That's why we need to
understand the mechanism.

With such cards, I suggest that the card has a zero floor limit [1], and
will only work with online POS terminals (i.e. those that have to get a
real-time authorisation) - if the terminal is offline, the transaction
will be declined. I'm sure I've read something like that somewhere.
(This would make them functionally similar to Visa Electron cards, so
why the Electron brand has been deprecated in favour of Visa Debit I'm
not entirely clear on.)

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[1] Possibly the incorrect terminology.