An ALARM is a device that produces a sound or signal to alert people of danger or to call them to attention. The term 'siren or bell' is often used to refer to an ALARM, as these are the two most common types of alarms. A siren is a loud, high-pitched noise that can be heard from a distance, while a bell is a lower-pitched sound that is usually heard from a closer range. Both sirens and bells are used to alert people to danger or to call them to attention.