Fire alarm wiring is regulated by NFPA 72 (not the NEC for most of it) and requires specific techniques and listed cable. The two main circuit classes: Class B is a simple loop - power goes out from the panel to all devices and terminates at the last device with an end-of-line resistor. Class A is a full loop that returns to the panel, providing supervision of the entire circuit and continued operation if there’s a single break.
Device types and their circuits: Initiating Device Circuits (IDC) connect detectors, pull stations, and monitoring inputs. Notification Appliance Circuits (NAC) power horns, strobes, and combination devices. Signaling Line Circuits (SLC) are the digital addressable communication circuits used in addressable systems. Each device on an addressable SLC has its own address and can report status individually.
Cable requirements: fire alarm cable must be listed for the application - FPL, FPLR (riser rated), or FPLP (plenum rated). In a plenum-rated ceiling, you must use FPLP or run in metal conduit. Fire alarm cables must be kept separate from other low voltage cables per NFPA 72. Getting these confused on a commercial job will fail your inspection and create a safety issue.