So ...
Barclaycard have introduced a slide-and-go payment system that allows a punter to leave the office via an alternative exit, purchase a banana in the supermarket and then head off, via the library, into the underground (or subway, as the cars all appear to
be driving on the right), where a single beep sees him slip-sliding all the way home, to ask for a towel in what seems to be an up-north accent.
I have performed a Griffo straw-poll and discovered that virtually everyone thinks that the advert is great, thinks that the waterslide is great, and thinks that the song is great, but no-one really has a clue about the message. Most spotted the BarclayCard
connection, and most recognised that by implication, it must relate to some sort of payment thingy, but no one actually spotted the payments being made - they are now all sitting in front of their tellys, waiting for 90 seconds of enlightenment, and the beeps.
Good advert though!
It got me thinking, and now I guess I need some help from someone very clever, as I just don't get it. I know that I can buy a banana, because I know how much a banana costs, assuming that bananas are sold by the banana and not by the pound, but even if
they are sold by the pound, I can weigh and pay, and that would simply mean slowing down a bit to check the weight. This is still not an issue, as I, and the POS systems, will know the total value of the transaction before the card is presented to the reader.
But how does that work on the underground? The card is presented to the reader before the reader knows how much to charge, and the reader cannot know how much to charge unless I tell it where I am going, and there isn't much chance of that since I am wizzing
through, in me trunks, waving the card as I pass. Something clever is surely going on here. The in-gate doesn't know where I am going, and the exit-gate doesn't care; even so, the in-gate must still charge me the right fare.
How does the subway system know by how much to debit my account?