tap-to-pay, beep

Welcome to #AskFlipScience, where we answer even the strangest, silliest questions with science!

This week’s question: How do tap-to-pay cards work?

If you’ve ever commuted in Metro Manila, sooner or later you’ll find yourself taking the train. You may also find yourself (naturally) needing to buy a ticket or have the option of using one of those tap-to-pay tickets (like the beep card).

But how do those things work, anyway? It’s all thanks to a nifty little invention called NFC (Near-Field Communication), and you might be seeing (and using) it more in the future.

I’d tap that

The beep card, like every other tap-to-pay device, works on NFC technology. This makes it possible for two devices to communicate with each other, depending on how close they are. This technology isn’t completely new, actually. Think of the QR and barcodes that you see in the supermarket, but only much more sophisticated.

There are typically two kinds of NFC devices:

Passive devices, which include tags, interactive signs, advertisements, and labels on shipping crates. Basically, anything that can broadcast data, but not receive or change the data that’s already on it. They’re useful for identifying stuff like where to put things in a warehouse, or giving you a link that you can scan using your phone to take you to a certain website.

On the other hand, active devices are ones that can store, transmit, and change date inside them. Some examples are smartphones, that card reader at your favorite coffee shop, or the touch-to-pay devices at convenience stores across the country.

So the train does this how…?

The cards that we use as train passes operate on a very basic NFC system. Power from the devices that scan the cards also provide the power for the data to be read, which is why the cards will only work once they’re near a payment or reloading terminal in the train.

Once that happens, the receiving device will transmit a tiny current that can activate the circuits inside the card, reading (or changing) the information as needed. This is also how it can keep track of how much you’ve spent on the card.

So the next time you go and tap something to pay anything, try to get used to the feeling. It might be how you’ll be paying for a LOT of things from now on.–MF

Cover photo: Yugatech


  • https://www.androidauthority.com/what-is-nfc-270730/
  • https://www.techradar.com/news/what-is-nfc

Author: Kyle Edralin

A writer, creative, and craftsman – Kyle (or as his friends call him, Phenex) trawls the internet for interesting science stories to share to the aforementioned friends. He has since decided to bring this pursuit to a much wider audience, and is working delivering this kind of information in a way that makes much more sense than his usual ramblings. He is also very fond of penguins.