System Sensor B200S-LF-WH — intelligent addressable low frequency sounder base in white, producing a 520 Hz ±10% square wave fundamental to meet the NFPA 72 sleeping space requirement. Accepts a compatible plug-in addressable sensor head, which is ordered separately.
The sounder base “listens in” to the communication between the attached sensor head and the fire alarm control panel and adopts the same address as the detector, but presents itself as a distinct device type on the loop. The panel can therefore command one sounder, or a group of sounders, and tailor volume, tone and group to the specific event. Two volume levels are available — nominally 85 dBA high and 75 dBA low — along with Continuous, ANSI Temporal 3, ANSI Temporal 4 and March Time tones, with custom tone patterns on some panels. The base recognizes the System Sensor synchronization protocol, so it can form part of a general evacuation signal alongside System Sensor horns, horn strobes and chimes when fed from a supply or panel output that generates System Sensor synchronization pulses. A separate mounting plate installs on a range of junction box sizes and allows all connections to be pre-wired, avoiding surface-mount boxes; two retaining screws lock the housing to the plate, and a mechanical locking feature prevents removal of the attached sensor head. The low frequency output targets sleeping occupants: research shows a fundamental near 520 Hz is the most effective at waking people, including those with mild to severe hearing loss.
Specifications
| Model |
B200S-LF-WH (white; “-WH” suffix denotes white, “-IV” ivory) |
| Type |
Intelligent addressable low frequency sounder base |
| Fundamental frequency |
520 Hz ±10%, square wave or equivalent |
| Sensor head |
Sold separately |
| External supply voltage |
16 to 33 VDC (VFWR) |
| External supply standby current |
550 µA maximum |
| Alarm current, high volume |
70 mA max @ 33.0 VDC; 90 mA max @ 24.0 VDC; 140 mA max @ 16.0 VDC |
| Alarm current, low volume |
15 mA max @ 33.0 VDC; 20 mA max @ 24.0 VDC; 25 mA max @ 16.0 VDC |
| SLC operating voltage |
15 to 32 VDC |
| SLC standby current |
300 µA maximum, base only — add the sensor head’s own draw |
| Sound output, high volume |
Greater than 85 dBA minimum, UL reverberant room at 10 ft, 24 V, continuous tone |
| Sound output, low volume |
Greater than 75 dBA minimum, UL reverberant room at 10 ft, 24 V, continuous tone |
| Tones |
Continuous, ANSI Temporal 3, ANSI Temporal 4, March Time; custom tones with some panels |
| Base diameter |
6.875″ (17.46 cm) |
| Base height |
2.0″ (5.08 cm) less sensor |
| Shipping weight |
0.60 lb (272 g) |
| Operating temperature |
32°F to 120°F (0°C to 49°C) |
| Operating humidity |
10% to 93% RH, non-condensing |
| Wire gauge |
12 to 24 AWG, SEMS screws |
| Junction boxes |
Single gang, double gang, 3.5″ octagonal, 4.0″ octagonal, 4.0″ square, 4.0″ square with 3.0″ mud ring |
| Listings |
UL 268 and UL 464 |
Installation notes
-
Alarm current goes up as voltage goes down: at high volume the base draws 70 mA at 33 V but 140 mA at 16 V — double. Size the notification power supply and standby battery from the worst-case end-of-line voltage under load, not from the 24 V figure, or a long circuit will brown out in alarm.
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Low frequency costs current: the -LF base draws far more than the standard B200S, which is a flat 35 mA at high volume. Do not carry a B200S calculation over to a B200S-LF design.
-
Two separate circuits: the base needs an external 16–33 VDC supply for the sounder in addition to the 15–32 VDC SLC connection. The sounder is not powered from the signaling line circuit.
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The 300 µA SLC standby figure is base only: add the attached sensor head’s standby current when calculating loop loading.
-
Head not included: this is a base. Order a compatible addressable sensor head, and confirm the pairing on the manufacturer’s Base/Sensor Cross Reference Chart — the base’s effective operating temperature range follows the sensor fitted to it.
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Confirm the panel protocol: the Silent Knight intelligent bases datasheet lists the B200S-WH and B200S-LF-WH as SK protocol devices. Verify the base, head and panel combination before ordering rather than assuming any addressable panel will drive it.
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Synchronization needs a capable source: the base joins a general evacuation signal only when connected to a power supply or panel output that generates System Sensor synchronization pulses.
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Metric boxes not supported: the junction box guide lists 50 mm, 60 mm, 70 mm and 75 mm boxes as not suitable for B200S series bases. Box depth also depends on base and wire size.
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Pre-wire the plate: the separate mounting plate lets every connection be made before the sounder housing goes on, and it locks to the housing with two retaining screws for tamper resistance.
Related models
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B200S-WH — standard-frequency white sounder base; 35 mA max at high volume, 15 mA at low volume
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B200S-LF-IV — same low frequency base in ivory
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B200SR-LF-WH — low frequency sounder base for retrofit applications, fully compatible with existing B501BH series sounder base installations
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B224RB-WH — relay base, one Form C contact, short (60–100 ms) or long (6–10 s) delay
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B224BI-WH — isolator base that segments the SLC during a short circuit and restores automatically
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M02-04-00 — test magnet; M02-09-00 test magnet with telescoping handle
Specifications taken from the System Sensor data sheet “B200S/B200S-LF Intelligent Sounder Bases,” document SPDS53602 (02/15), and the Silent Knight data sheet “Intelligent Bases,” document SK-61045:B (7/8/2019). Manufacturer specifications are subject to change without notice.
