Notes:
Banish those unwanted beasties this Summer with this insect repellant circuit from Graham Maynard. Consisting of a phase locked loop (CMOS 4047) wired as a 22KHz oscillator, this is sure to repell those creepy crawlies.  The output is further amplified by a pair of complimentary output transistors and drives a Motorola 3.25 inch Piezo. Current drain is around 120mA so an external power supply is recommended. This page is coated in "Insect green".