Police will disperse gangs of teenagers with an electronic gadget which sends out a high frequency noise that can be heard only by young people.

The machine has not so far been used in Sussex.

Dubbed the Mosquito, the device will be used by officers in Lancing as part of Operation Save The Streets, which aims to tackle long-running problems with vandalism and antisocial behaviour.

The device, which costs £600, sends out an irritating ultra high-pitched sound and can be used over a range of 20 metres.

It is said to work only on youngsters because people suffer progressive hearing loss, of higher frequencies first, from the age of 20 onwards.

Police in the Adur district are also promising thousands of pounds will be spent increasing high-visibility patrols in Lancing.

Traders claim vandals are ruining the area and intimidating neighbours while yobs are roaming Lancing's main shopping area smashing windows.

Many elderly people have declared South Street a no-go area at night.

Adur police commander Chief Inspector Sharon Rowe said: "I understand and sympathise with these concerns.

"I have now got the money to pay for Operation Save The Streets, which will be launched in Lancing next week.

"Police will not just be there to make arrests but to act as a deterrent and to talk to local teenagers about other ways they could be spending their time.

"Officers will be on the streets every day and night for the next two months.

"We will also be using a device called Mosquito which transmits a high-frequency sound similar to the insect.

"It can only be heard by people under the age of 20 and they find it very annoying. It will be mounted on a patrol car and will be used to encourage groups of teenagers to move away from the area."

Martin Johnson, 63, leaseholder of The Cycle Station, in South Street, said: "As shopkeepers, we do not know on a daily basis which one of us is going to find their shop vandalised.

"The cafe next door has had its windows smashed for the second time in a month.

"The elderly, as well as shopkeepers, are continuously intimidated and none of us know how much longer we can stay in business."

Mr Johnson said in the past six years there had been three smash-and-grab raids at his store.

He has also been the victim of an arson attack and one of his staff quit because they could no longer stand the intimidation.

Kris Pillai, of jewellers Facets, said he was trying to encourage more traders to join the local Shopwatch scheme.

It provides a radio link so businesses can keep each other and the police informed about known troublemakers in the area.

He said: "I know about 20 of the kids who roam around here have antisocial behaviour orders against them.

"The first day I came to work here I saw the cafe had all its windows smashed in and it is terrible that it keeps happening.

"When I get off the train in the morning I see big groups of youths hanging around in the Co-op car park next to the station.

"You do feel intimidated but you just have to put your head down, say nothing and walk through them."

Some pensioners said they would not venture into South Street at night.

Sylvia Lower, 71, and husband Gordon, 80, live nearby but said they felt intimidated by the yobs.

Mrs Lower said: "If it wasn't for them we would go out at night but they are very intimidating.

"They smash the windows at the Co-op and Somerfield but by the time the police car gets here they have run off."

Billed as an "ultrasonic teenage deterrent," the Mosquito is claimed by manufacturers Compound Security to be "the most effective tool in our fight against antisocial behaviour."

Inventor Howard Stapleton said this would be the first time the Mosquito had been used in Sussex.

With an effective range of between 15 and 20 metres it relies on the medical phenomenon known as presbycusis or age-related hearing loss which begins at the age of 20 but is usually only thought to be significant to the elderly.

It makes it possible to generate a high frequency sound of 18 to 20 Hz that is audible only to teenagers.

The system, thought to be harmless even with long term use, was first used at a Spar shop in Barry, South Wales, where owner Robert Gough said: "Either someone has come along and wiped the troublemakers off the face of the earth or it's working."