An alarm device or system of alarm devices gives an audible, visual or other form of signal about a problem or condition. Alarm devices are often outfitted with a siren.
Alarm devices include:
burglar signals, designed to warn of burglaries; this is often a silent alarm: the police or guards are warned without indication to the burglar alarm, which increases the chances of catching him or her.
alarm clocks can beep, buzz or ring off as an alarm at a set time to wake a person up or for other reminders