This free split-screen tool lets you explore a fire alarm system as both a 3D building model and a live system architecture schematic at the same time. Place and inspect devices on the building while watching how they wire into the signaling and notification circuits back to the panel. It's a hands-on learning aid for fire alarm designers, NICET candidates, and electrical engineers studying how device layout, circuits, and the riser come together under NFPA 72.
The two synchronized views cover layout and wiring together:
• Interactive device placement — drop and inspect smoke/heat detectors, pull stations, and horn/strobes on the 3D building. • Signaling line circuits (SLCs) — the addressable data loops that connect initiating and addressable devices back to the FACP. • Notification appliance circuits (NACs) — the powered circuits driving the horns and strobes. • Riser diagram — the vertical schematic showing how circuits travel floor-to-floor. • Cross-highlighting — click a device in the 3D view or a node in the architecture view and both highlight, so you can see exactly where each device sits on its circuit.
Designing a layout means placing initiating devices to satisfy NFPA 72 coverage and spacing, then wiring them onto circuits. Smoke and heat detectors are spaced on a grid (typically a 30 ft nominal spacing for smooth ceilings, adjusted for ceiling height, beams, and airflow). Notification appliances are placed so audible and visible (strobe candela) coverage reaches every occupiable area. Devices are then assigned to SLCs and NACs, each device gets an address, and the riser shows how those circuits stitch the floors back to the FACP.
1. Orbit, zoom, and pan the 3D building to position your view. 2. Place or select devices on the building and watch them appear on the architecture schematic. 3. Click any device or circuit node to cross-highlight it in both views and trace its path along the SLC or NAC back to the panel and up the riser.
Start from the NFPA 72 nominal spacing — typically 30 ft on center for spot-type smoke detectors on a smooth, flat ceiling — then adjust for ceiling height, slope, beams/joists, and HVAC airflow, which can reduce the usable spacing. Detectors are placed so no point on the ceiling is more than 0.7 times the nominal spacing from a detector, and additional rules apply for corridors, sloped ceilings, and high-airflow areas.
An SLC is the addressable communication loop that connects intelligent initiating devices and modules to the FACP. Each device has a unique address, so the panel can poll devices individually, read their status and sensitivity, and pinpoint the exact device in alarm or trouble — unlike a conventional zone, which only reports a group of devices.
Class B wiring is a single-path circuit: a wire fault (open) downstream of the break leaves those devices unmonitored. Class A wiring returns the circuit back to the panel, providing a redundant path so the circuit keeps operating even with a single open, because the panel can drive the loop from both ends. Class A offers higher survivability but uses more wire and panel capacity.
Addressing assigns each addressable device a unique identifier on its SLC. The address lets the FACP know precisely which device generated a signal, display its location, and track per-device status like sensitivity drift or maintenance alerts — which speeds response and greatly simplifies troubleshooting compared with conventional zoned systems.
An SLC is a low-power data circuit carrying addressed signals between devices and the panel (inputs and addressable modules). A NAC is a higher-power output circuit that delivers operating voltage to notification appliances — horns and strobes — when the panel declares an alarm. One senses and communicates; the other powers the alert.