Glossary Terms and Definitions Beginning with the Letter F

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.

3. Fahrenheit temperature scale.

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 A Fourier transform (FT) converts a signal from the time domain (signal strength as a function of time) to the frequency domain (signal strength as a function of frequency). It shows the signal's spectral content, divided into discrete bins (frequency bands).

The Fast Fourier Transform is a common algorithm for Fourier transforms. It is more efficient (faster) than the DFT, Discrete Fourier Transform.

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.
FlexSound FlexSound describes a set of digital audio signal processing blocks used in Maxim's products to provide or enhance audio functions such as compression, limiting, or equalization.

FlexSound® processor is a fully programmable digital audio signal processing system that includes a programmable DSP core, hard-wired digital macros, and an associated memory architecture.

FlexSound is a registered trademark of Maxim Integrated Products, Inc.
  1. A signal line is said to be "floating" if it is not connected to any voltage supply, ground, or ground-referenced signal source.


    • An open-drain, high-impedance (hi-z) output when in the off (hi-z) mode
    • In microcomputer systems, a data or address bus may, at times, be undriven (floating). This is permissible because control signals indicate when data is valid, so users of the bus know when the signal can be ignored.

  2. One form of non-volatile memory device is achieved via floating gates. The gate of a MOSFET has no connection, allowing charge to remain indefinitely. The gate charge is changed using Fowler-Nordheim tunneling or hot-carrier injection. EPROM, EEPROM, and flash memory are examples.
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
Fourier Transform See FFT
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 graph depends on the sampling rate and the size of the data record (the number of acquisition points). The number of frequency points or lines or bands in the power spectrum is NRECORD/2, where NRECORD is the number of signal points captured in the time domain.

The first frequency line in the power spectrum always represents DC (frequency=0). The last frequency line can be found at fSAMPLE/2 - fSAMPLE/NRECORD. Frequency lines are spaced at even intervals of fSAMPLE/NRECORD. They are commonly referred to as frequency bins or FFT bins. Bins can also be computed with reference to a data converter's sampling period:

Example: We apply a sampling frequency of 82MHz and take 8192 records. The frequency bin is 10kHz.
Frequency Diversity In radio systems, Frequency Diversity spreads a signal across multiple channels by transmitting multiple versions of the signal on different frequencies.
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