Littelfuse FB9L, Universal Lamp Alarm Relay, 120-230VAC

In stock
Regular price $513.55
Rated voltage

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The FB9L is a universal lamp alarm relay designed to sense the failure of flashing LED beacon lamps. It will monitor the operation of one to eight beacons connected to a single flasher and/or auxiliary modules and the operation of the flasher. The FB9L output relay energizes when one or more lamps fail. All monitored lamps must be the same wattage and voltage. The 0.5A solid-state output energizes when a flasher failure is sensed.


When a LED beacon lamp fails, the FB9L senses a decrease in current flow. After a 10s lamp failure trip delay, the isolated SPDT (4-5-6) and non-isolated SPNO (3-1) relay contacts energize. These contacts are used to indicate a beacon failure has occurred. The “L” onboard LED indicator flashes green during the trip delay and glows red after the output relay energizes. Connected to a site monitoring system, it provides remote beacon monitoring required by FAA-AC No: 150/5345-43E.

The FB9L also monitors the operation of the flasher. If the flasher remains in the ON or OFF condition for more than 6s the solidstate output energizes and the “F“ flasher failure, onboard LED glows red. This output is normally used to energize an external flasher bypass relay. The contacts of the bypass relay are used to route voltage around the failed flasher and to indicate an alarm condition.

Note: In a single flasher, single beacon system, if the beacon lamp fails, zero current flow is detected. This will cause the flasher failure output to energize after 6s and then the beacon failure outputs after 10s. This is normal operation and can be expected anytime zero current is flowing through the monitored conductor.

Pre-order 6-8 Weeks

Input Voltage (V) 120 - 230 VAC
Input Tolerance (%) ±15%
Input AC Line Frequency (Hz) 50/60
Output Form 3 total: 2 relay and 1 solid state
Output Load Rating (VA) One isolated SPNO relay rated 5 A @ 240 Vac or 30 Vdc resistive - 1/4 hp @125 Vac - 1/2hp @ 250 Vac; One SPDT relay rated at 10 A @ 240 Vac or 30 Vdc resistive - 1/4 hp @125 Vac - 1/2 hp @ 250 Vac; One solid-state line voltage output rated 0.5 A steady and 5A inrush
Trip Delay Range Flasher failure: Fixed at 6 s; -0/+40;
Lamp failure: Fixed at 10 s; -0/+40%
Indication Lamp failure (Red): LED glows when one or both lamps fail;
Flasher failure (Red): LED glows when the flasher fails
Circuitry Encapsulated
Operating Temperature -40° to 60°C (-40° to 140°F)
Storage Temperature (F/C) -40° to 85°C (-40° to 185°F)
Mounting Method Surface mount with one #10 (M5 x 0.8) screw
Termination Type IP20 screw terminals for up to 14 AWG (2.45 mm²) wire or two 16 AWG (1.3 mm²) wires
Dimensions 3 H x 2 W in. (76.7 x 51.3 mm)