"Haddock" wrote in message
...
TC wrote:

Oysters might be affected when placed on shop counters that use RF
security
stickers (the counter 'busts' the chip in the sticker by pounding it
with a
very strong radio wave).


My girlfriend recently started setting off the RF security detector
things at the doors to shops. We have been very puzzled about it, and
now I suddenly wonder if it's her Oyster card. The problem started
about the same time she bought it.

Surely not?

It is possible - since both RF tags and Oyster use radio waves for power.
The two fundamental differences are that an RF tag has a resistor and oyster
a smartchip - and a RF tag has a spiral loop and the oyster a single loop*.
The RF tag idea is that the resistor changes the radio frequency (which gets
retransmitted) and then this is picked up by the sensors (I guess in a
similar way to a TV van). We have a lot of trouble at work with simple loops
of cable (ie. stuff we actually sell!) setting off the alarms occasionaly -
so I guess the resistor is not required and anything can produce the right
frequency - so it might be possible.

You could try to 'investigate' by seeing if the store really uses RF tags or
magnetic labels. Failing that try waving the oyster at a sensor....

Anyhow, my original point was - can the chip be 'busted' in the same fashion
as the resistor? (this would seem to be a serious design flaw...)

--
TC

* I think - since I've only seen the inside of a SmartRider (similar bus
card technology) not an Oyster.