The Lifesystems Survival Whistle is the world's most powerful whistle. Made from a toughened plastic material, the Survival Whistle is an essential part of any outdoor or mountain survival kit. A whistle can be used to alert people if you are in distress. The internationally recognised distress signal is 6 blasts of the whistle with a 1-minute break and then repeated. The reply is 3 blasts with the same pause.