thumb|Fire alarm in [[Magnuson Park]]
An alarm device is a mechanism that gives an audible, visual, combination, or other kind of alarm signal to alert someone to a problem or condition that requires urgent attention.
Etymology
The word alarm comes from the Old French a l'arme meaning "to the arms", or "to the weapons", telling armed men to pick up their weapons and get ready for action because an enemy may have suddenly appeared.
The word alarum is an archaic form of alarm. It was sometimes used as a call to arms in the stage directions of Elizabethan dramas. The term comes from the Italian all'armi and appears 89 times in Shakespeare's First Folio. Often explained as the off-stage sounds of conflict or disturbance, recent research suggests a bell or drum may have been used to rouse soldiers from sleep. In addition, false alarms may acclimatise people to ignore alarm signals, and thus possibly to ignore an actual emergency: Aesop's fable of The Boy Who Cried Wolf exemplifies this problem.
A false alarm is one of the most significant issues with conventional alarm systems. They can be triggered for several reasons, such as the movement of pets, typing in the wrong security codes, or loud sounds from windows or doors. In the case of fire alarms, aerosol sprays, smoking, or burning food can all lead to a false alarm.