Countries establish their public warning systems to warn their population against common danger. Historically, typical dangers included a military danger (war, bombing, rocket attacks) and danger of natural disasters (flood, tsunami, earthquake). Modern industrial production has brought a danger of industrial disasters and the current situation in the world has brought a danger of terrorist and war attacks.
As for the emergency situations caused by such dangers, countries, which are represented by relevant institutions, have developed a variety of emergency plans to instruct the persons in charge/the first responders on what measures and procedures are to be taken in such situations. These measures also include the warning procedures established by national acoustic warning systems. Despite the existence and usage of other forms of notifying the public of an impending danger, for example, television, radio, and mobile phone, the warning systems based on electronic sirens with their own communication infrastructures represent the most reliable and effective method of mass warning in endangered areas.