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Side of a prism, seen most often in crystal glass chandeliers and other wall fixtures.


Fade Rate

The time it takes each zone/channel to arrive at the next scene dependent on the degree of change in light level.


Fade Time

The time it takes all zone/channels to fade from one lighting scene to another with all zones/channels arriving at the next scene at the same time.



Fahrenheit is the temperature scale proposed in 1724 by, and named after, the German physicist Daniel Gabriel Fahrenheit (1686–1736).


Scientific unit of temperature.

Conversion from
kelvins degrees Celsius °C = K − 273.15
degrees Celsius kelvins K = °C + 273.15
kelvins degrees Fahrenheit °F = K × 1.8 − 459.67
degrees Fahrenheit kelvins K = (°F + 459.67) / 1.8
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Firmware is programming inserted into programmable read-only memory, thus becoming a permanent part of a computing device. Firmware can be distributed like other software and, using a special user interface, installed in the programmable read-only memory by the user.



Flow Sensor

A device for sensing the rate of fluid flow. Typically, flow sensor is the sensing element used in a flow meter, to record the flow of fluids.



Fluorescence (Fluorescent) is a luminescence that is mostly found as an optical phenomenon in cold bodies, in which the molecular absorption of a photon triggers the emission of a photon with a longer (less energetic) wavelength. The energy difference between the absorbed and emitted photons ends up as molecular rotations, vibrations or heat. Sometimes the absorbed photon is in the ultraviolet range, and the emitted light is in the visible range, but this depends on the absorbance curve of the particular material.


Within the context of lighting control, Fluorescence is typically associated with fluorescent lamps.


Fluorescent Lamps

A fluorescent lamp or fluorescent tube is a gas-discharge lamp that uses electricity to excite mercury vapor. The excited mercury atoms produce short-wave ultraviolet light that then causes a phosphor to fluoresce, producing visible light.


Unlike incandescent lamps, fluorescent lamps always require a ballast to regulate the flow of power through the lamp. However, a fluorescent lamp converts electrical power into useful light more efficiently than an incandescent lamp; lower energy costs offsets the higher initial cost of the lamp.




A type of ceiling fan that mounts directly to a junction box, and do not have a down-rod to maintain maximum clearance from the floor.



Unit of illuminance (light falling on a surface). One lumen falling on one square foot equals one-foot candle. Also, a measurement of the amount of light reaching a subject.


Flame-In Kit

Part of a recessed downlight connected to the electrical circuit and generally installed when the ceiling is open. The electrified mounting form or housing which supports the optical assembly of a recessed fixture. Frame-In Kits are of various types according to the nature of the construction and the lamp.


free topology, LON

A connection scheme for the communication bus that removes traditional transmission line restrictions of trunks and drops of specified lengths and at specified distances, and terminations at both ends. Free topology allows wire to be strung from any point to any other, in bus, daisy chained, star, ring, or loop topologies, or combination. It only requires one termination anywhere in the network.


Frost & Sullivan

Frost & Sullivan, is a consulting company established in 1961. Frost & Sullivan serves clients that includes Global 1000 companies, emerging companies, and the investment community, by providing industry coverage that reflects a global perspective and combines ongoing analysis of markets, technologies, economoetrics, and demographics.