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Glossary Terms and Definitions Beginning with the Letter F

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F	1. Farad(s): Unit of capacitance. 2. f in lower case is the standard abbreviation for femto, a metric prefix for 10 to the -15.
fA	Femtoampere(s): 10 to the -15 Ampere; a millionth a nanoampere.
Facility Data Link	See FDL
Fail-Safe	A technique used in RS-485 interface transceivers which forces the output to a predefined state in the event of a line short or open circuit.
Fan Control	See Fan Controller - Linear
Fan Controller - Linear	An integrated circuit that varies the speed and airflow of a cooling fan using a variable voltage in response to temperature or system commands.
Fan Controller - PWM	An integrated circuit that varies the speed and airflow of a cooling fan using a pulse-width-modulated (PWM) voltage in response to temperature or system commands.
Farad	See F
Fast Fourier Transform	See FFT
Fault Blanking	A function that ignores a fault for a predetermined period. This is done to eliminate nuisance fault indication.
Fault Tolerant	Will tolerate excessive voltage during a fault condition.
FB	Feedback
FCD	Fan count divisor
FCR	Fan conversion rate
FDD	Frequency-division duplex
FDDI	Fiber Distributed Data Interface: A standard for transmitting data on optical fiber cables at a rate of around 100,000,000 bits-per-second (10 times as fast as 10 Base-T Ethernet; about twice as fast as T-3).
FDL	Facility data link: Embedded communications channel in ESF DS1 framing. Used to convey both bit-oriented and message-oriented signals.
FDM	A method for carrying multiple channels of information on one channel by dividing the available bandwidth among the channels.
FE	Functional equivalent (in component cross-reference data); also field engineer; also framing error
FEC	Forward Error Correction: A technique for detecting and correcting errors from imperfect transmission by adding a small number of extra bits. FEC allows optical transmission over longer distances by correcting errors that can happen as the signal-to-noise ratio decreases with distance.
femto	See F
Femto Base Station	A femto base station (also called an Access Point Base Station, femtocell, femtobasestation or femto basestation) is an in-home base station. Like a standard base station, it connects cell phone voice and data to the cell phone network, but it serves a smaller area (the home). A femto base station benefits the service provider because it offloads cell tower traffic. Subscribers benefit from superior signal strength, due to the proximity of the unit -- especially where a cellular signal is weak or not available. Femto base stations augment the normal network and replicates the usual telecommunications infrastructure. Connection to the cell phone network is provided by VoIP over the Internet. More on femto base stations and information on Maxim's femto base station chipsets.
femto basestation	See Femto Base Station
femtobasestation	See Femto Base Station
femtocell	See Femto Base Station
FET	Field-Effect Transistor: A transistor in which the voltage on one terminal (the gate) creates a field that allows or disallows conduction between the other two terminals (the source and drain). There are three varieties: The JFET (Junction Field-Effect Transistor); the MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor); and the MESFET (Metal-Semiconductor Field-Effect Transistor). The FET is one of two major kinds of transistor, the other being the Bipolar Junction Transistor.
FFT	Fast Fourier Transform: An algorithm for converting data from the time domain to the frequency domain; often used in signal processing.
FG	Fan gain
FHSS	Frequency Hopping Spread Spectrum: A transmission technology in which the data signal is modulated by a narrowband carrier signal which changes frequency ("hops") over a wide band of frequencies. The hopping seems random but is prescribed by an algorithm known to the receiving system.
Fiber Channel	See Fibre Channel
Fiber Distributed Data Interface	See FDDI
Fiber-to-the-node	See FTTN
Fibre Channel	A highly-reliable, gigabit interconnect technology that allows concurrent communications among workstations, mainframes, servers, data storage systems, and other peripherals using SCSI and IP protocols. It provides interconnect systems for multiple topologies that can scale to a total system bandwidth on the order of a terabit per second. (The standardized spelling is "fibre channel" but often misspelled as "fiber channel.")
Field Programmable Gate Array	See FPGA
Field-Effect Transistor	See FET
Fieldbus	See PROFIBUS
FIFO	First-In First Out: A type of memory that stores data serially, where the first bit read is the first bit that was stored.
Finagle's Law	See Murphy's Law
FireWire	Apple Computer trademarked name for the IEEE 1394 serial interface standard: A high-speed interface between computers and peripherals such as external disk drives, cameras, and camcorders. Also referred to by Sony trademarked name, "I-Link."
First In First Out	See FIFO
FIT	Failures in time: See FIT calculator: /tools/calculators/index.cfm/path/qa/calc_id/qafits
Flash ADC	See Flash ADCs
Flash ADCs	An analog-to-digital converter that uses a series of comparators with different threshold voltages to convert an analog signal to a digital output.
FM	Frequency Modulation: A modulation method in which the carrier frequency changes with the input signal amplitude.
FM Modulator	See VCO
FOC	Fields oriented control
Foldback Current Limit	A circuit which reduces the current limit once the device enters current-limited operation. Commonly seen on RS-422/RS-485 drivers and some power circuits.
Foldback Mode	See Foldback Current Limit
folded-frequency	See Aliasing
Force-Sense	Measurement technique in which a voltage (or current) is forced at a remote point in a circuit; then the resulting current (or voltage) is measured (sensed).
Forward Converter	A power-supply switching circuit that transfers energy to the transformer secondary when the switching transistor is on.
Forward Error Correction	See FEC
FOX	Fast-on oscillator
FPBW	Full-power bandwidth
FPGA	Field Programmable Gate Array: A family of general-purpose logic devices that can be configured by the end user to perform many, different, complex logic functions. It is often used for prototyping logic hardware.
FR	See Frame Relay
Frame Relay	A high-speed, packet-switched data communications service similar to X.25. Frame relay is a leading contender for LAN-to-LAN interconnect services, and is well suited to the burst-intensive demands of LAN environments.
Framer	A device used to align/synchronize to an embedded framing pattern in a serial bit stream. Once synchronized and data fields are properly aligned, overhead bits for alarms, performance monitoring, embedded signaling, etc. may be extracted and processed.
Framers	See Framer
Framing	See Framer
Frequency Bin	The frequency range and resolution on the frequency axis of a spectrum (FFT) graph usually depend on the sampling rate and the size of the data record (the number of acquisition points). The number of frequency points or lines in the power spectrum is N_RECORD/2, where N_RECORD is the number of signal points captured in the time domain. The first frequency line in the power spectrum always represents DC. The last frequency line can be found at f_SAMPLE/2 - f_SAMPLE/N_RECORD. Frequency lines are spaced at even intervals of f_SAMPLE/N_RECORD, commonly referred to as frequency or FFT bins. Bins can also be computed with reference to a data converter's sampling period: Bin = f_SAMPLE/N_RECORD = 1/(N_RECORD × Δt_SAMPLE)
Frequency Division Multiplexing	See FDM
Frequency Hopping	See DSSS
Frequency Hopping Spread Spectrum	See FHSS
Frequency Modulation	See FM
Frequency Shift Keying	See FSK
Frequency Synthesizer	A frequency synthesizer is an electronic circuit that uses an oscillator to generate a preprogrammed set of stable frequencies with minimal phase noise. Primary applications include wireless/RF devices such as radios, set top boxes, and GPS.
FS	Full scale; frame sync
FSC	Fan-speed control
FSK	Frequency Shift Keying: A method of transmitting digital data by shifting the frequency of a carrier signal to represent binary 1s and 0s.
FSO	Full-span output
FSOTC	Full-span output temperature coefficient
FSR	Full-scale range
FTC	Fan tachometer count
FTCL	Fan tachometer count limit
FTTB	Fiber-to-the-business
FTTH	Fiber-to-the-home: A method for broadband data (voice, Internet, multimedia, etc.) delivery to the home via optical fiber. Contrast with FTTN (fiber-to-the-node) which uses fiber up to a node outside the home and uses copper to bring the data into the home.
FTTN	FTTN is "Fiber-to-the-node." There are two technologies for delivering broadband: Fiber-to-the-node (FTTN) uses fiber to bring data to a node and uses copper to bring the data into the home. Fiber-to-the-home (FTTH) brings fiber all the way into the home.
Fuel Gauge	See Battery Fuel Gauge
Full Duplex	A channel providing simultaneous transmission in both directions.
Full-Duplex	See Full Duplex