Notification appliances are the visible and audible face of any fire alarm system. When an alarm activates, horn strobes and speaker strobes are what alert occupants to evacuate — making them both safety-critical and one of the most frequently replaced components in any commercial fire alarm system. The Simplex TrueAlert series represents one of the most widely installed lines of notification appliances in North America, and knowing the right model for each application is essential for fire alarm technicians and facilities managers alike.
The Simplex 4906 Series: TrueAlert Notification Appliances
The Simplex TrueAlert 4906 series encompasses a full range of horn strobes and speaker strobes designed for commercial and institutional fire alarm applications. These devices are designed to work with Simplex TrueAlarm panels and are widely used in hospitals, schools, universities, and office buildings. Key models include:
- 4906-9127: Multi-candela horn strobe in red. This is the workhorse of the TrueAlert line — a wall-mount combination horn/strobe with field-selectable candela output.
- 4906-9103: Strobe only in white, for applications requiring visual-only notification (typically used in conjunction with a separate speaker).
- 4906-9151: Multi-candela speaker strobe for systems with voice evacuation capability.
- 4906-9153: Speaker strobe in white, for voice evacuation applications where color coding requires white appliances.
Multi-Candela Settings and ADA Requirements
One of the most important features of TrueAlert notification appliances is field-selectable candela output. Rather than stocking multiple fixed-candela devices, the multi-candela design allows a single appliance to be configured for the correct intensity at installation time. This simplifies inventory and ensures compliance with ADA and NFPA 72 spacing requirements.
The Simplex 4906-9127 Multi-Candela Horn Strobe supports selectable output levels including 15, 30, 75, and 110 candela (model-dependent). ADA requires that visible notification appliances in corridors be installed at 80-96 inches above the finished floor and spaced according to NFPA 72 Table 18.5.5.4.1 — which specifies minimum candela based on room size. Multi-candela devices allow the installer to match the installed device to the room spacing without special ordering.
For voice evacuation systems, the Simplex 4906-9151 Multi-Candela Speaker Strobe combines a UL-listed fire alarm speaker with an ADA-compliant synchronized strobe in a single device, reducing both installation labor and device count.
Strobe Synchronization
NFPA 72 requires that all visible notification appliances within a single occupant space be synchronized to flash simultaneously. Unsynchronized strobes in the same field of view can trigger photosensitive seizures and are a code violation. TrueAlert strobes use the Simplex synchronization protocol, which is controlled by the Simplex panel or a compatible synchronization module. When replacing a TrueAlert strobe, always verify that the replacement device supports the same synchronization protocol as the installed system.
Wiring and Circuit Supervision
TrueAlert notification appliances are wired on supervised NAC (Notification Appliance Circuit) loops. The panel monitors the circuit for opens, shorts, and ground faults. Each circuit must be terminated with an end-of-line (EOL) resistor, with the value specified in the panel installation documentation. When adding or replacing appliances, ensure the circuit load (current draw) does not exceed the panel or booster power supply NAC output rating.
Speaker strobes add audio frequency current to the NAC wiring, which requires attention to circuit impedance in addition to DC current. Always calculate speaker circuit impedance per the Simplex panel guidelines when installing or replacing TrueAlert speaker strobes.
Replacement Considerations
When replacing a TrueAlert appliance, match the following specifications:
- Color: Red or white — must match the existing installation for ADA and code compliance.
- Type: Horn strobe, strobe only, speaker strobe, or speaker only.
- Candela setting: Match or exceed the original installed setting.
- Mounting: Wall mount (most common), ceiling mount, or outdoor-rated where applicable.
Where to Buy Simplex TrueAlert Appliances
Life Safety Consultants stocks TrueAlert horn strobes and speaker strobes for Simplex systems. Browse the full Simplex notification appliance catalog at LSC for current availability on 4906 series devices. With genuine Simplex parts and fast shipping, LSC keeps your notification appliance replacements straightforward and code-compliant.
