Alarm Systems An alarm is anything that warns people when something is wrong. When an alarm is activated, someone can take immediate action to correct the problem. Some alarms are very simple. A barking dog can be a warning that an intruder has entered the area. Most alarms used today are much more complex. Alarm systems are usually made up of many mechanical or electrical parts. Different sites will have different alarm systems and you will have to learn about the specific one used at the site where you work. You should know how to arm, disarm, and reset an alarm system. You should also know how to recognize obvious problems and how to test the system to see if it is operating well. The following information will give you a general overview of alarm systems, so it will be easier to understand the one that is used at your site.