Bus/Tram/subway card in Lisbon/Porto

Not sure why it would be frustrating? It a transit card with a contactless RFID chip inside of it, similar to London's Oyster card. When entering a station or bus you simply put the card next to the reader and wait for the green light.

I brought this up because I read, in the Lonely Planet guide, how there are times when the devices on the trams or buses did not work. Sometimes the green light never came on. People thought they had paid, but actually didn't. One family was taken of the tram by a policeman. This won't stop me from using the cards, since it's obviously cheaper than taxis. Thanks for the post.

Don't sweat it, during my time in both cities the cards worked flawlessly.