The Mosquito or Mosquito alarm is an electronic device used to deter loitering by young people by emitting sound at high frequency, in some versions so it can only be heard by younger people. The devices have attracted controversy on the basis of human rights and discrimination concerns. The device is marketed as a safety and security tool for preventing youths from congregating in specific areas. As such, it is promoted to reduce anti-social behaviour such as loitering, graffiti, vandalism, drug use, drug distribution, and violence. In the UK, over 3,000 have been sold, mainly for use outside...