The Complete Handbook of Home Alarm Systems

Chapter 1: Understanding Home Alarm Systems

A home alarm system, in its most basic form, is a network of sensors connected to a central control panel that is programmed to respond to specific changes in the environment. The purpose of that response is to do one of two things: alert people in the home that an event is occurring, or notify a remote party, such as a monitoring center or the homeowner's mobile phone. While the term "alarm" often implies a loud siren, the real value of a modern system lies in the communication and automation that happens alongside, and often before, the audible noise.

To understand what these systems actually do, it helps to step through a concrete scenario. Let's say a homeowner has an exterior door at the back of the house. A typical entry sensor consists of two parts: a magnet and a reed switch. The magnet is mounted on the door itself, and the reed switch is mounted on the door frame. When the door is closed, the magnet holds the reed switch in a closed circuit state. When the door opens, the magnet moves away, the circuit opens, and the sensor transmits a signal to the control panel. If the system is armed and the control panel is expecting the door to be closed, it immediately registers an alarm condition. From there, the panel can sound the siren, send a push notification to the owner's phone, and if the system is monitored, it can place