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Public motor siren
Alarm at the border post

An alarm is an acoustic or visual emergency signal . In a more general sense, an alarm is any warning that draws attention to an imminent danger and calls for increased vigilance, or the state of acute danger and increased readiness (“issue / lift an alarm”). The word was borrowed from Italian ( allarme ) into German in the 15th century and goes to the military wake-up call 'all'arme!' ("To arms!") Back; When the initial sound was omitted, the word noise ("noise, noise") developed from this a little later .

Example fire alarm

If a fire breaks out in a building , fire alarms can emit acoustic signals . Corresponding reactions would now take place from the building personnel, i.e. leaving the building on appropriate escape routes . At the same time, a fire alarm system could alert the fire brigade and rescue service .

Triggering an alarm - alerting

An alarm can either be triggered by personal observation of a damaging event or automatically . The common feature of all alarms is that the message about a damaging event or a danger that is passed on by one person, by too few people or by people who are not trained in dealing with the damaging event, is passed on to a responsible body. This is also known as an initial alarm. Furthermore, alarming is also to be understood as the post-alarm, in which the alarm is distributed from this point to other affected points or persons.

The siren is still used in connection with radio reports to reach whole population groups . When notifying individuals, the telephone or a radio service is predominantly used. When alerting certain groups, such as emergency services, radio alarm receivers have become established, but SMS alerts are also used (often in addition). It should be noted that the SMS message arrives less reliably than the radio message, and will be unreliable, especially in the event of a disaster. A transmission confirmation can be obtained for the SMS message.

Device alarm

An alarm can also be triggered with the aid of measuring devices if a warning threshold is reached or exceeded. In the case of alarm dosimeters in radiation protection or explosimeters in the event of pollution accidents, for example, an alarm tone sounds if the people would enter an area that would pose too high a burden for them. When searching for leaks on gas lines, the gas detector emits a beep or a control lamp flashes if there is escaping gas.

Important devices also give a simple alarm if their internal function is not working properly. If the battery is too weak to operate the device, this is often indicated acoustically or optically.

Alarm plans

Adapted to the individual events (depending on the alarm level), exact alarm plans are created that describe exactly how reactions should take place ( schedule as well as alarm and release order ). In this context, organizations are called upon to make a call to suit their situation (determination of resources and personnel).

Requirements for an alarm system

An alarm system in particular has to work reliably. This is why certain minimum requirements must be placed on such a system at the planning stage.

  • The alarm must be transmitted very quickly and without delay.
  • An alarm must be able to reach the group concerned and be identifiable by them.
  • The system needs to be operational around the clock, all year round.
  • The alarm system must ensure that the auxiliary staff can be reached by covering the entire area and penetrating the building through the radio signal (if possible into the underground car park).
  • The false alarm rate must be low, otherwise desensitization occurs and unnecessary costs arise.
  • If it is not triggered automatically, it must be easy to handle and operate.
  • An acknowledgment option must be able to ensure delivery of the alarm.
  • In the event of delivery errors, additional participants should be notified of escalations .
  • Particularly when alarms are sent via radio, there must be no overlapping by other networks that could disrupt the network or trigger false alarms.
  • The cost factor and simple maintenance should not be underestimated today.

Alarms in process control technology

Alarms are of particular importance in a control room (for chemical plants, power plants, energy distribution systems, etc.). The operator is “officially” informed that a limit value has been exceeded. No operator can claim that he has not received any information about a threatening condition.

A horn sounds and an indicator light is initiated. The operator must i. d. R. "acknowledge". Only then is the signaling switched off. The indicator light stops flashing and changes to steady light. If the process variable that triggered the alarm is in the good range again, the indicator light goes out.

When planning a control center, you have to weigh up which alarms are useful and necessary. If too many alarms are planned, the frequent horn horns create stress for the operators. A distinction is therefore made between initial and follow-up alarms. Subsequent alarms do not trigger a horn and do not have to be acknowledged.

Many (badly planned) control centers have a far too high alarm rate (sometimes more than 2000 alarms per day and operator), which devalues ​​the alarm system and in extreme cases it becomes completely unusable. A good alarm philosophy can be achieved through systematic alarm management . At least parts of the system that are switched off must not generate an alarm.

Historic bugle


There have been alarms since people lived in groups; In the Middle Ages there were the tower keepers who sounded the alarm and rang the fire bell . Before the attack by enemy troops, so-called chalk fires were lit for larger areas in Central Europe .

alarms At the beginning of the 19th century, when a fire broke out, certain residents had to fetch the fire engine immediately . Not every village had one. A fire walker had to request another fire pump if necessary. In many localities of the Duchy of Nassau , when a fire was detected, the teachers of the village had to ring the bell and sound the alarm for the committee drum. The committee ensign had to have the committee (a slightly military-trained guard) manned all exits of the place so as not to let anyone out during the fire except fire walkers and those who were assigned to fetch the syringe. All residents able to work had to rush to the scene of the fire with a filled bucket and stand in double rows after the nearest water (e.g. stream, fire pond). “The bucket flew through the long chain of hands.” Following the express orders of the authorities, care had to be taken “that the women who were only confused by their lamentation were brought into the ranks”. Refusal to obey the commando, unauthorized removal from the scene of the fire or deliberate damage to the extinguishing equipment was punishable by severe physical punishment. The items rescued from the scene of the fire were closely guarded in a fire-proof location by the committee's teams. Anyone who tried to steal in the confusion was bound by the guard in the event of trespassing, put down by the things in order to receive punishment immediately after the fire was extinguished. But for those who distinguished themselves in the rescue work through zeal, courage and fearlessness, a reward of up to four talers was offered.

See also

Web links

Wiktionary: Alarm  - explanations of meanings, word origins, synonyms, translations

Individual evidence

  1. Alarm in: German Foreign Dictionary . 2nd edition, volume 1: A-prefix – antiquity. De Gruyter, Berlin and New York 1996, pp. 347-349;
    Alarm. In: Digital dictionary of the German language .
  2. noise. In: Digital dictionary of the German language .
  3. ^ Franz-Josef Sehr : The fire extinguishing system in Obertiefenbach from earlier times . In: Yearbook for the Limburg-Weilburg district 1994 . The district committee of the Limburg-Weilburg district, Limburg-Weilburg 1993, p. 151-153 .