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Practice Listening: Select Missing Word
ID: #4178
Short
Battery
Transcript:
He and his team have indeed designed a battery-free phone. It looks like a circuit board, with touch-responsive numeric buttons. And it runs on just a few microwatts of power, which it harvests from light, and from the radio signals eminating from a nearby wireless base station. The team achieved the battery-free, energy-efficient design by ditching two of the power-hungry features of modern cell phones. One, the test unit skips digital to analog conversion. And two, it does not generate its own wireless signals to make calls. Instead, in receiving mode, it absorbs incoming radio waves from the base station, and converts them directly into vibrations of its speaker. In sending mode, it uses the vibrations of its on board microphone to change the way radio waves are reflected back to the base station. And it worked - to make a skype call.
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