18WuD2x

fixed-frequency oscillator • flange 287
cillator can be self-excited or controlled (crystal,
fork, magnetostriction, etc.).
fixed-frequency receiver A receiver that is pretuned
to receive signals of one frequency.
fixed-frequency transmitter A transmitter that is
pretuned to radiate signals of one frequency.
Such a transmitter can contain a self-excited or
crystal-controlled oscillator.
fixed inductor A nonadjustable inductor (i.e., one
having an unalterable value of inductance).
fixed-length record A record in which word or
character size is constant. Compare VARIABLE
LENGTH RECORD.
fixed logic Applicable to computers or peripherals
whose logic can only be altered internally by
changing connections.
fixed memory A nonvolatile readout computer
memory that can only be altered mechanically.
fixed placement file A file that has been allocated
a fixed location in storage.
fixed-point system A notation system in which a
single set of digits represents a number, and the
radix point (in the decimal system, the decimal
point) can only be placed in one position for the
value being expressed. Also see FLOATING-
POINT CALCULATION.
fixed resistor A nonadjustable resistor (i.e., one
having an unalterable value of resistance).
fixed-sequence robot A robot that performs one
task or set of tasks, making exactly the same
movements every time. The sequence is programmed
in the robot controller via firmware.
Many assembly robots and toy robots are of this
type. Compare FLEXIBLE AUTOMATION.
fixed station A radio station operating from a stationary
point; one that is not mobile.
fixed-step potentiometer A potentiometer whose
output is varied in one or more discrete steps by
fixed-resistor sections. Also see POTENTIOME-
TER.
fixed wireless 1. A cellular communications network
in which some, or all, of the end users are at
fixed locations. This is increasingly popular as an
alternative to conventional hard-wired telephone
and Internet access. 2. The use of wireless equipment,
such as cell phones and wirelessmodem–equipped
computers, at fixed (rather
than mobile or portable) locations.
fixed word length Applicable to the organization of
information in storage in which each computer
word stored has a fixed number of characters or
bits.
fixture A piece of hardware used in equipment setups
(e.g., microwave couplers, joints, sections,
etc.).
fL Abbreviation of FOOT-LAMBERT.
flag 1. A piece of information added to a data item
that gives information about the data item. 2. A
bit added to a character or word to delineate a
field boundary. 3. An indication that an operation
is complete and need not be done by the program.
4. An indicator identifying the members of mixed
sets. 5. A character that signals the presence of
some condition (e.g., an error flag indicates that a
data item caused an error).
flag event A program condition that causes a flag
to be set.
flag line An input pulse to a microprocessor that
depends on specific external instructions. Indicates
a certain condition or change of state.
flagpole antenna 1. Any of several vertical UHF or
VHF antennas consisting of a radiator mounted
atop a coaxial pipe or cable (see, for example,
COAXIAL ANTENNA). It takes its name from its
resemblance to a flagpole. 2. A vertical antenna
formed by shunt-feeding a pole already in existence,
such as a flagpole. This can be done to
conceal the antenna.
Coaxial
feed line
Whip to coax
center conductor
Center
insulator
Pipe to coax
outer conductor
Base
insulator
flagpole antenna, 1
flag terminal A form of terminal that does not require
soldering for electrical contact. A protruding
“flag” is crimped around the conductor.
flame alarm A (usually photoelectric or thermoelectric)
device or circuit for detecting a flame and
actuating an alarm.
flame control A (usually photoelectric or thermoelectric)
device or circuit for sensing and automatically
controlling the height of a flame, such
as a gas pilot.
flame-failure control A FLAME CONTROL that automatically
cuts off the fuel if the flame goes out.
flame microphone A microphone in which two
electrodes in a flame undergo a change in electrical
resistance when the flame is influenced by
sound waves, thus modulating current passing
between the electrodes.
flange 1. A flat, protruding edge used for fastening
a connector or plug to the chassis of a piece of
equipment. 2. In a waveguide, a coupling used for
connection to another section of waveguide, or to
a horn or other external device.