The tangle of cables and plugs needed to recharge today's electronic gadgets could soon be a thing of the past. US researchers have outlined a relatively simple system that could deliver power to devices such as laptop computers or MP3 players without wires. The concept exploits century-old physics and could work over distances of many metres. Although the team has not built and tested a system, computer models and mathematics suggest it will work. Resonance" [is] a phenomenon that causes an object to vibrate when energy of a certain frequency is applied. "When you have two resonant objects of the same frequency they tend to couple very strongly," Professor Soljacic [explained]. Resonance can be seen in musical instruments. "When you play a tune on one, then another instrument with the same acoustic resonance will pick up that tune, it will visibly vibrate," he said. Instead of using acoustic vibrations, the team's system exploits the resonance of electromagnetic waves. Electromagnetic radiation includes radio waves, infrared and X-rays. The team from MIT is not the first group to suggest wireless energy transfer. Nineteenth-century physicist and engineer Nikola Tesla experimented with long-range wireless energy transfer, but his most ambitious attempt - the 29m [it was actually 187 feet] high aerial known as Wardenclyffe Tower, in New York - failed when he ran out of money. A UK company called Splashpower has also designed wireless recharging pads onto which gadget lovers can directly place their phones and MP3 players to recharge them.