Insect Repellent

This insect repellent circuit will repel insects such as mosquitoes, flies and cockroaches from your home or yard effectively. circuit uses a specific frequency to disrupt the insect so the insect will go away from this circuit.

This insect repellent circuit can be placed inside or outside the home (for speakers). If you want to put the whole circuit on the outside of the house, make sure the circuit is in a safe place, especially when it rains.

This circuitry consists of a PLL (Phase Looked Loop) oscillator circuit using a CMOS 4047 with a frequency of 22 KHz. Current drain is around 120mA. So, external power supply is recommended for better results.

Source: http://www.zen22142.zen.co.uk/Circuits/Misc/insecrep.html