Tech Terms Glossary
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Fb: The resonant tuning frequency of a vented speaker cabinet.
Fc: The resonant frequency of a sealed speaker cabinet.
F connector (short for "RF connector"): Coaxial connector used mainly for CATV, CCTV and satellite TV systems.
Feedback: When a transmitted signal is loops back and is retransmitted through a system, often causing a saturated and/or distorted result. This happens in audio when a microphone "hears" the sound coming from the speakers it's playing through, causing squealing distortion. This also happens when a camcorder "sees" the video signal from the video screen it's playing through, causing overly-bright or saturated color, "ghosts" and brightness of the picture.
FG Servo Motor: A frequency generator in the motor produces a signal dependent on motor rotation. This is compared to a reference signal and the motor is controlled so that the two signals are the same. Compared to an electronic governor motor, the FG motor has less speed deviation or drift and is less affected by temperature.
Fiber Optics: Process by which flexible glass fibers are used to conduct energy. It is valuable in the coupling of multi-stage image intensifiers.
Field: One half of a frame, consisting of either the odd or the even numbered lines, 60 fields are transmitted every second. flange back: The distance from the flange of the lens (beginning of the lens mount) to the focal plane. C-mount lenses have a flange back distance of 17.526mm vs. 12.5mm for CS-mount.
Fill: The acoustic absorption added inside a speaker cabinet to suppress unwanted resonances and sometimes to increase the apparent volume of the cabinet.
Flange Back: The distance from the flange of the lens (beginning of the lens mount) to the focal plane. C-mount lenses have a flange back distance of 17.526mm vs. 12.5mm for CS-mount.
Flying Erase Head: A feature available on selected VHS VCRs, on 8mm and Hi8 VCRs, and on camcorders. The unique design of these recording heads prevents electronic noise during videotape recording transitions, for glitch-free insert editing.
FM (Frequency Modulation): Method of audio signal broadcast transmission used for radio.
f-number: The f-number indicates the brightness of the image formed by the lens, controlled by the iris. A smaller f-number means a brighter image.
Focal Length: The distance from the center of the lens to a plane at which point a sharp image of an object viewed at an infinite distance from the camera is produced. The focal length determines the size of the image and the angle of the field of view seen by the camera through the lens. That is the distance from the center of the lens to the pickup device.
Foot-Candle (FC): It is the light intensity (illumination) of a surface one foot distant from a source of one candela. It is equal to one lumen per square foot. (1FC = 1 lm ft2). The foot-candle is the unit used to measure incident light.
Fp: The free-air resonant frequency of a passive radiator.
Frame: The total area of the picture which is scanned while the picture signal is not blanked.
Frequency-agile: means that the operating (modulation) frequency is adjustable to suit different applications.
Frequency Response: (Example, 30-20,000 Hz) Describes the audible range of frequencies that an audio system will reproduce. (Note: All else being equal, the lower the low number, the better the bass response and the higher the high number, the better the treble response.)
Front Porch: The portion of the composite video signal which lies between the leading edge of the horizontal blanking pulse and the leading edge of the corresponding synchronizing pulse.
Fs: The free-air resonant frequency of a speaker driver. The frequency at which an object tends to vibrate. For example, although a bell can be externally driven to vibrate at different frequencies, it will always naturally tend to vibrate at it's given tuned tone, or resonant frequency.
f-stop: A term used to indicate the speed of a lens. The smaller the f-number, the greater is the amount of light passing through the lens.
F3: The point at which the signal strength of a loudspeaker falls 3 decibels below the loudspeaker's rated SPL, as the frequency decreases.
Fully-Automatic Turntable: A turntable that, when turned on by the operator has all the necessary functions to lift the tone arm from rest post and place it on the lead-in groove and return it to the rest post when it reaches the record's end.
Full-Logic Controls: With this feature, all of the mechanical operations inherent to audiocassette receivers are controlled through a microprocessor chip, for smoother, faster, more accurate response and easier transitions from function to function.
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