Denmark
The national siren system in Denmark is comprised of 1,078 Whelen WPS-2800 series sirens which are distributed and sold by HSS Engineering (a distributor & reseller of Whelen sirens in Denmark), located on rooftops or masts depending on the area. It is tested annually, on the first Wednesday of May at noon.
Each signal lasts 45 seconds. The alert, or Go indoors signal, utilizes the Indoor Protection tone from the European tone set, while the all clear, or Danger is over signal, utilizes the All Clear tone.
Sirens are installed in areas with a population of more than 1,000 people, allowing the system to reach 80% of the national population. The remaining 20% are alerted by mobile sirens mounted on police cars.