The COMPACT ELECTRONIC POCKET WHISTLE blows itself with a push of a button. This whistle emits an ear shattering 120 decibel whistle for as long as you hold the button. This can be used as an emergency locator, a sports whistle, dog training, a safety alarm, etc. At just 4 inches in length, this compact whistle is easy to carry in your pocket or purse. Requires four LR44 batteries (included).