Alarm is an electronic product, which reminds or warns us that we should take some action in the form of sound, light and air pressure to prevent or prevent the consequences of an event. Alarm is divided into mechanical alarm and electronic alarm. With the progress of science and technology, mechanical alarms are increasingly replaced by advanced electronic alarms, which are often used in the fields of system failure, safety precautions, transportation, medical rescue, emergency rescue, induction detection and so on, and are inseparable from social production. Such as door magnetic sensor and gas induction alarm.
According to the different use environment, alarms can be divided into the following categories:
1. Home alarm.
2. Business alert.
3. Fire alarm.
4. Temperature alarm.
5. Smoke alarm.
6. Gas alarm.
7. Sound and light alarm.
8. Double network alarm.