On 29 Jan, 14:31, ticketyboo wrote:
On Jan 29, 11:33*am, "Gretchen Lauss" wrote:



I do wonder though what will happen as more and more debit/credit cards get
contactless tech - will they interfere with each other, and not just with
Oyster cards?

There are two basic maybe two effects he

- Cards stored together disrupt the collection of power by all of
them.

- But, if more than one of those cards collects enough power to
operate, the terminal then has to use the anti-collision mechanism
specified by the standard (ISO 14443 in the case of Oyster and bank
payment cards - and also for ITSO cards) in order to identify all the
operating cards, send the ones that it doesn't want to communicate
with to sleep, and then carry out its transaction.

Of course, if only one card collects enough power to operate, and it
is not the right one, that creates a different problem. And if the
right one starts up and then another starts up later, that can also
disrupt the transaction.

And the terminal does not implement the anti-collision function...

I have a Smartlink (similar to Oyster) card for PATH in New Jersey.
It works fine with my Oyster card next to it, but the Oyster will
never read unless I take the Smartlink card away. Not too much of a
problem in this case, since I'm seldom going to want to use both on
the same day, but it could be a real problem as these cards become
more common if you need to carry several around with you, and they
interfere with each other. Clearly they don't have to do this, as the
Smartlink readers will quite happily ignore the Oyster card.