The outdoor alarm, which is for important messages to the public, is tested four times a year and today is the time again.
During the autumn, Ljusdal suffered from several thefts of the horns.
In one of the cases, a suspected perpetrator was identified using images from a surveillance camera.
The horn was then found in the tailgate of an A tractor.
- It was connected to the car's sound system and functioned as some type of amplifier, says Peter Nystedt.
Anders Johannesson, head of unit at MSB, takes the thefts seriously.
- It creates white spots on the map where we cannot warn the public of a possible danger, he says.
In Ljusdal, it is unclear where the other horns have gone, but it is suspected that more may be in A-tractors.
- We have received indications that they can be found in this particular environment, says Peter Nystedt.
Hear more about the thefts in the video above.