Reference · Circuits & Power
Notification Appliance CircuitNAC
The circuit that powers horns, strobes, speakers and bells. Normally held at reverse polarity for supervision and switched to alarm polarity (or driven with audio) when the panel goes into alarm. Sized by voltage drop and total appliance current.
NFPA 72: Chapter 12, Chapter 18 (Notification Appliances)
Section numbers vary by edition — confirm in the edition your AHJ has adopted.
Read more in these guides
Fire Alarm Wiring & Circuits, SimplifiedCircuit type, class, and pathway integrity decide whether a system keeps working when a wire is damaged. Here's the plain-language version.Fire Alarm Voltage Drop, ExplainedThe last strobe on a long circuit sees less voltage than the panel supplies. Here's why voltage drop happens and how designers stay within limits.