According to the news, what makes this credit card different from conventional ones is ______.

A credit card that only works when it hears its owner’s voice has been developed by U. S. scientists. Researchers hope that the device, which comes with a built-in voice recognition chip and microphone, will be a weapon in the battle against credit card fraud. Even if thieves know a card’s password and personal identification number, they will still have to copy the owner’s voice accurately. The trial-card was created by scientists as B card in California U. S. The first version is three times as thick as a normal credit card. But researchers believe smaller chips will allow the card to slim down to a more conventional size. The card is apparently the first to put a voice recognition chip, a microphone, speaker and a battery into a credit card. To use the card, the owner first presses a button, and hears the prompt: say your password. If the password is correct and spoken by the right person, the card emits an identification signal which is processed by a computer connected to the Internet. Researchers hope to get the card to handle ten transactions per day for two years before its non-replaceable battery runs out.