Chapter 3 of NFPA 731 contains general definitions used in the standard. It is important to understand the different types of “Signals” in a security system.

Signals are indicators of a specific status within the security system. Some signals might report an unauthorized event at the protected premises while other signals may indicate that there is a fault in a monitored security circuit or component.

Supervisory signals indicate the need for action in connection with the supervision of guard tours, environmental or other nonintrusion related issues in the system.

Below is a sample of NFPA 731. For the complete section, see the actual NFPA 731 text at NFPA.ORG. Once there, click on the free access link to the latest edition of NFPA 731.

3.3.24 Signal. An indication of a condition communicated by electrical, visible, visual, audible, wireless, or other means.

3.3.24.1 Alarm Signal. A signal that results from the manual or automatic detection of an alarm condition.

3.3.24.2 Supervisory Signal. A signal indicating the need for action in connection with the supervision of guard tours or environmental or other nonintrusion monitored point or system.

3.3.24.3 Trouble Signal. A signal that results from the detection of a trouble condition.