wave and go credit cards

I’ve seen the ads but forget the term. They show someone in a coffee shop or quicky mart that just waves his card over the terminal to pay for stuff.
How does that work?
How does it know who’s card is paying for what?
How close do you have to be to make it work?

I’ve used wave and go cards to open locks on doors, any you can sometimes keep the card in your pocket and just turn toward the sensor.

Sure it’s a credit card?

Generally, my experience with these things is “treat 'em as cash. Lose it, and… well… lose it.” Generally, “wave and go” cards seem to be limited stored value cards. Some credit card companies (Visa springs to mind) offer debit cards which act as credit cards, so maybe it’s something like that.

The other possibility is that Joe Richguy with his gold credit card can use this function, but on an entirely different credit limit to his main one (how many coffees can a pickpocket drink in a day?), and is expected to telephone and cancel the card if it’s lost or stolen.

All the above is just a WAG though. I’m curious myself.

RFID tag. Basically the reader puts out a radio frequency that powers a tiny circuit in the card which sends out your card’s information when the card is moved near the reader. RFID tags

The same way the card machine knows when you swipe your card now. It’s keyed in by the register, or automatically done. It charges whoever swipes their card near the reader.

Probably depends on the specific reader/card, but the Speedpass at Mobil generally needed to be within an inch or less of the reader.

http://www.usa.visa.com/personal/cards/contactless/index.html?it=c|%2Fpersonal%2Findex.html|Visa%20Contactless
http://www.mastercard.com/us/personal/en/aboutourcards/paypass/index.html

These links may be helpful to you. I don’t know if Discover or American Express have anything similar, but these are the RFID enabled cards offered by Visa and MasterCard.

American Express Blue has RFID.

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Source: http://storefrontbacktalk.com/story/102906contactless.php
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Assuming the above to be accurate, one must balance their need for convenience against a desire of security for personal information. My life doesn’t run so fast that such a convenience would ever outweigh my desire to protect against identity theft.