British schoolchildren have created high-frequency ringtones that adults cannot hear. Unheard by teachers mobile phone calls are now distributed directly at classes. Students adapted the Mosquito signal to their needs, which is used in shopping centers to scare off groups of teenagers. This signal effectively copes with its task, because ultra-high sounds are heard only by teenagers and are not heard by people over 20 years of age. Teenagers can now rejoice: their favorite SMS and even calls they can take right during classes.

YYY: Do British schoolchildren not know about vibrators?