DETECTOR BASES
Showing all 8 results
Showing all 8 results
Fire Alarm Detector Bases – Simplex & Silent Knight | In Stock | QuickShipFire
QuickShipFire stocks 8 professional fire alarm detector bases for Simplex TrueAlarm and Silent Knight SD505 addressable systems covering every base type a commercial fire alarm contractor needs: standard mounting bases, supervised relay bases, sounder bases, and isolation bases. Every in-stock unit ships same-day from our California warehouse when ordered before 2:30 PM PST.
A detector base is the permanently wired half of an addressable fire alarm sensor installation. The base mounts to a standard 4-inch electrical box and connects to the Signaling Line Circuit (SLC). The sensor head smoke, heat, or CO – then twists or plugs onto the installed base. When you replace a failed sensor head, only the head is touched; the base stays wired in the ceiling. Choosing the correct base type from day one prevents costly return visits.
How to Choose the Right Fire Alarm Detector Base
Choosing the wrong base is one of the most common installation mistakes in commercial fire alarm work. Before ordering, confirm three things:
- Brand / system family – Simplex TrueAlarm 4098-series bases are NOT interchangeable with Silent Knight SD505-series bases. They use different physical mounting geometry and different SLC protocols.
- Required function Do you need a plain mounting base (standard), a relay output base (relay base), a built-in sounder base (sounder base), or a short-circuit isolation base (isolation base)?
- Sensor compatibility Not every base accepts every sensor head. Cross-reference your sensor model against the compatibility tables below before ordering.
Simplex TrueAlarm 4098 Base Types – Quick Reference
| Model | Type | Key Function | Compatible Sensors | Price |
| 4098-9780 | Relay Base | Form C relay output — elevator recall, door holders, fan shutdown | 4098-9601, 4098-9602, 4098-9714, 4098-9733 | $95 |
| 4098-9789 | Standard Base | Plain mounting + SLC connection — no relay or sounder | 4098-9601, 4098-9602, 4098-9714, 4098-9733 | $35 |
| 4098-9791 | 4-Wire Addressable Base | Connects 4-wire conventional detectors to addressable SLC | 4-wire conventional sensors | $95 |
| 4098-9792 | Standard Base | Plain mounting + SLC connection — same function as 4098-9789 | 4098-9601, 4098-9602, 4098-9714, 4098-9733 | $50 |
| 4098-9794 | Sounder Base | Built-in 88 dBA sounder + remote LED terminals | 4098-9601, 4098-9602, 4098-9714, 4098-9733 | $75 |
Silent Knight SD505 6″ Base Types – Quick Reference
| Model | Type | Key Function | Compatible Detectors | Stock Status | Price |
| SD505-6IB | Isolation Base | Short-circuit isolation for Class A SLC loops | SD505-PHOTO, SD505-HEAT | Out of stock | $95 |
| SD505-6RB | Relay Base | Form C relay — elevator recall, door closure | SD505-PHOTO, SD505-HEAT | Out of stock | $85 |
| SD505-6SB | Sounder Base | Built-in sounder for localized alarm audio | SD505-PHOTO, SD505-HEAT | IN STOCK |
$115
|
Fire Alarm Detector Base Types Explained
Standard / Plain Bases – 4098-9789 & 4098-9792
A standard base provides nothing beyond a mechanical mounting point and electrical SLC connection. It is the correct choice for the majority of detector locations corridors, offices, classrooms, and storage rooms — where no relay or sounder output is needed. The 4098-9789 ($35) and 4098-9792 ($50) are functionally identical; the difference is minor physical construction. Always match the exact model number to the base already in the building when ordering replacements.
Relay Bases – 4098-9780 & SD505-6RB
A relay base adds a built-in Form C dry contact relay that the fire alarm control panel switches independently via programming. Common applications: elevator recall (at lobby detectors to recall elevator cars on fire alarm), magnetic door holder release (allowing fire-rated doors to close), and HVAC fan shutdown at individual zone level. A relay base eliminates the need for a separate addressable control module at that location saving an SLC address and reducing wiring cost.
Sounder Bases – 4098-9794 & SD505-6SB
A sounder base incorporates a built-in piezoelectric audible element that activates during alarm, providing localized audio notification at each detector. Sounder bases are widely used in hotels, hospitals, dormitories, and assisted living facilities where per-room audibility is required by code – NFPA 72 sleeping area requirements often mandate 75 dBA at the pillow level. A sounder base at the ceiling detector satisfies this without the cost of running a separate notification circuit to every room.
Isolation Bases – SD505-6IB
An isolation base includes a built-in short-circuit isolator that automatically disconnects a faulted SLC segment while keeping the rest of the loop operational. Required in Class A (Style 7) SLC wiring topologies where loops pass through multiple fire compartments or floors. NFPA 72 mandates isolation in these configurations. Installing isolation bases on every device in a Class A system eliminates the need for separate standalone isolation modules in junction boxes.
Panel-to-Base Compatibility Quick Reference
Never mix Simplex and Silent Knight bases in the same system. Match the base family to your panel brand.
| Your Fire Alarm Panel | Base Family to Use | Protocol |
| Simplex 4100ES | 4098-9780, 4098-9789, 4098-9791, 4098-9792, 4098-9794 | IDNet / MAPNET II |
| Simplex 4010ES | 4098-9780, 4098-9789, 4098-9791, 4098-9792, 4098-9794 | IDNet / MAPNET II |
| Simplex 4007ES | 4098-9780, 4098-9789, 4098-9791, 4098-9792, 4098-9794 | IDNet / MAPNET II |
| Silent Knight 5208 | SD505-6IB, SD505-6RB, SD505-6SB | Silent Knight SLC |
| Silent Knight IFP-2100 | SD505-6IB, SD505-6RB, SD505-6SB | Silent Knight SLC |
| Silent Knight IFP-50 / IFP-75 | SD505-6IB, SD505-6RB, SD505-6SB | Silent Knight SLC |
Brands We Carry in Detector Bases
- Simplex (Johnson Controls) TrueAlarm 4098-series bases (4098-9780, 4098-9789, 4098-9791, 4098-9792, 4098-9794). The 4098-series is standard for Simplex 4100ES, 4010ES, and 4007ES panels the most widely installed Simplex addressable panels in US commercial buildings since 1995. Browse all Simplex products →
- Silent Knight (Honeywell) – SD505-series 6″ bases (SD505-6IB, SD505-6RB, SD505-6SB). The SD505 family is standard for Silent Knight 5208, IFP-2100, and IFP-series panels, widely used in hotels, schools, and light commercial buildings. Browse all Silent Knight products →
