Earlier this year, Swindon installed devices that emit a high-pitched ultra sonic tone that only young people under the age of about 20 around problem areas of the town to deter anti-social behaviour.

It was hailed as a great success, except that teenagers turned the idea on its head by recording the sound to use as a ringtone for mobile phones that they can hear, but teachers and parents cannot.

Now Opera Telecom, in conjunction with Meodi Media, is selling Mozzy Tones, the official Mosquito Ringtone, for £3.00 at http://www.mozzytones.co.uk.

Iain Kerr, Director of Melodi Media, says, "Kids will be able to text each other silently, with the notification of an arriving message being effectively hidden from any adults, but very obvious to the recipient".

The tone is a frequency of 17 kilohertz.