German high school transmits lessons by lights

　　The idea of using LED ceiling lights to transmit Wi-Fi-like Internet signals continues to move slowly forward, as a German high school is deploying a prototype Li-Fi system in a specially equipped classroom to deliver lessons to students' laptops.

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　　The school in Stuttgart, called Hegel-Gymnasium, is using the room to teach a broad range of subjects — everything from history to information technology. Five ceiling lights send wireless signals to small tabletop boxes, which then transmit to laptops via Ethernet cable. Each light covers 2m2, and each box can support up to four laptops or other devices.

　　Li-Fi, short for light-fidelity, is a two-way form of visible light communication (VLC), an emerging technology that uses invisible modulations in LED light frequencies to embed data. Proponents say that it will open up a vast amount of spectrum that will be needed as Wi-Fi waves saturate. Wi-Fi is a radio technology.

　　Li-Fi enthusiasts also note that Li-Fi is not susceptible to interference the way Wi-Fi is (although Li-Fi requires line of sight), it does not emit electromagnetic radiation, and it is more secure.