Scientists from the University of Washington in Seattle created a prototype mobile phone that does not require a battery for calls. The device receives the necessary energy thanks to rarefied air

The key parts of the system are outside the phone. So, the base station connects to the cellular network using Skype. In this case, the prototype can operate at a distance of 15 meters from the base station. On the device are the keys, as well as a small LED-display.

Conversations on such a device are similar to talks on the radio. To switch between listening and talking, you need to press the button. In addition, there is strong interference when talking.

In the course of the project, the engineers developed a backscatter technology that reflects incoming radio waves. That even such a technology has become too energy-intensive for such a project. "The conversion of human speech into digital signals consumes a lot of energy," said one of the creators of the prototype Vamsi Talla.

Scientists also turned to Soviet developments, which were used during the Cold War. The publication tells about the bug that was installed at the US Ambassador to the USSR: the device was activated at a certain frequency of radio waves and used their energy for work.

Energy can be obtained from ambient light through solar panels or photodiodes, as well as turn high-frequency television or Wi-Fi signals into electricity. However, the problem is that with these methods it is possible to get several tens of microwatts, while the traditional cell phone uses about 800 milliwatts when calling.