London Banter - View Single Post - London buses to offer contactless payment card option from tomorrow(12/12/12)

Roland Perry · December 18th 12, 11:32 AM posted to uk.transport.london

In message , at 12:21:03 on Tue, 18 Dec
2012, d remarked:
The problem with doing it for every transaction is that the card is
allowed to be removed from the RF field *before* the terminal has even
started its validation sequence.

In which case the transaction fails. Whats the problem?

But the transaction doesn't fail - that's the normal mode of use.

Huh? So the money gets deducted before any validation is done?

No, the money is only deducted if the validation is successful.

The retailer's and the cardholder's account will be updated to indicate
a successful transaction; and a failed transaction will be flagged at an
online terminal (some milliseconds after the card has been removed). A
failed transaction at an offline terminal becomes a bad debt (for the
retailer/bank) and sorting that out is part of the swings and
roundabouts that permeates all card transactions (contactless or not).

The only thing that I believe doesn't happen, because it's basically a
read-only device, is the card being updated to indicate whether the last
transaction succeeded or not.

That's not too hard to understand is it?

--
Roland Perry