Police in the UK have given their backing to a gadget that sends out a high-pitched noise that can only be heard by those under 20.

However, because the body's natural ability to detect some frequency wave bands diminishes almost entirely after 20, adults are completely immune to the sounds.

The Mosquito, which is hoped will be used to move on teenage gangs hanging around shops is essentially a sounder unit that emits a very high (ultra-sonic) tone that is completely harmless even with long-term use.

The black box, which can be attached to the outside wall of shops, offices and homes, sends out 80-decibel bursts of pulsing sounds at up to 16khz.

According to the company, field trials have shown that teenagers are acutely aware of the Mosquito and usually move away from the area within just a couple of minutes.

Sounding like the bug that its named after or a badly played violin, the effective range is between 15 and 20 metres. The closer one gets to the unit the more effective it is.

The unit comes complete with a remote ON/OFF switch, so the unit can be turned on and off as required.

Those looking to scare away kids can buy their very own Mosquito or Sonic Teenager Deterrent to give it its proper name for £581.63 with a security cage to protect it at £41.13.

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