Reference · Circuits & Power
Initiating Device CircuitIDC
A conventional circuit that connects initiating devices (pull stations, smoke and heat detectors, waterflow switches) to the panel. Devices simply close or change the circuit; the panel knows a zone is in alarm but not which device. Supervised with an end-of-line device.
NFPA 72: Chapter 12 (Circuits and Pathways), Chapter 23
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.Class A vs Class B (and Class X) Fire Alarm Circuits, ExplainedClass A, B, and X describe how much a circuit can survive before it stops working. Here's what each designation actually buys you.