BACK RESISTANCE - The larger resistance value observed when you are
checking the resistance of a semiconductor .
BACKINGS - (See base film.)
BACKUP FILE - A copy of a program or data file to be used in the event
something happens to the original.
BALANCED MIXER - A waveguide arrangement that resembles a T and uses
crystals for coupling the output to a balanced transformer .
BALANCED PHASE DETECTOR - A circuit that controls the oscillator frequency
(afc) .
BANDPASS FILTER - A filter that allows a narrow band of frequencies to
pass through the circuit. Rejects or attenuates frequencies that are either higher or
lower than the desired band of frequencies .
BAND-REJECT FILTER - A tuned circuit that does not pass a specified band
of frequencies .
BANDWIDTH - The difference between the highest usable frequency of a
device (upper frequency limit) and the lowest usable frequency of the device (lower
frequency limit) - measured at the half-power points .
BARRETTER - A type of bolometer characterized by an increase in resistance
as the dissipated power rises .
BASE - The element in a transistor that controls the flow of current
carriers .
BASE - (1) A reference value. (2) A number that is multiplied by itself as
many times as indicated by an exponent. (3) Same as radix. (4) The region between the
emitter and collector of a transistor that receives minority carriers injected from the
emitter. It is the element that corresponds to the control grid of an electron tube .
BASE FILM - The plastic substrate material used in magnetic tape that
supports the coating.
BASE-INJECTION MODULATOR - Similar to a control-grid modulator. The gain
of a transistor is varied by changing the bias on its base .
BASIC (Beginners All Purpose Symbolic Instruction Code) - A high-level,
general-purpose programming language primarily used on microcomputers. See NAVEDTRA 10079,
Introduction to Programming in BASIC.
BATTERY - A device for converting chemical energy into electrical energy .
BATTERY CAPACITY - The amount of energy available from a battery. Battery
capacity is expressed in ampere-hours .
BAUD - A measurement of speed based on the number of code elements or
units per second .
BAY - Part of an antenna array .
BEAM - See LOBE .
BEAM-LEAD CHIP - Semiconductor chip with electrodes (leads) extended
beyond the wafer .
BEAM-POWER TUBE - An electron tube in which the grids are aligned with the
control grid. Special beam-forming plates are used to concentrate the electron stream into
a beam. Because of this action, the beam-power tube has high power-handling capabilities .
BEARING - An angular measurement of the direction of an object from a
reference direction, such as true north .
BEARING RESOLUTION - Ability of a radar to distinguish between targets
that are close together in bearing .
BEAT FREQUENCIES - Difference and sum frequencies, which result from the
combination of two separate frequencies .
BEAT FREQUENCY - The difference between the oscillator frequency and the
unknown audio frequency .
BEAT-FREQUENCY OSCILLATOR - An additional oscillator used in a receiver
when it is receiving a cw signal. It provides an audible tone .
BEL - The unit that expresses the logarithmic ratio between the input and
output of any given component, circuit, or system .
BER - (See bit error rate.)
BETA - The ratio of a change in collector current to a corresponding
change in base current when the collector voltage is constant in a common-emitter circuit
.
BEVERAGE ANTENNA - A horizontal, long-wire antenna designed for reception
and transmission of low-frequency, vertically polarized ground waves .
BIAS - Difference of potential applied to a vacuum tube or transistor to
establish a reference operating level .
BIAS CURRENT - Current that flows through the base-emitter junction of a
transistor and is adjusted to set the operating point of the transistor .
BIAS-INDUCED NOISE(See noise.)
BIDIRECTIONAL ARRAY - An array that radiates in opposite directions along
the line of maximum radiation .
BINARY - (1) A number system that uses a base, or radix, of 2. Two digits
(1 and 0) are used in the binary system. (2) Pertaining to a characteristic that involves
the selection, choice, or condition in which there are only two possibilities. (3) A
bistable multivibrator (flip-flop) is one example of a binary device .
BINARY CODE - A method of representing two possible conditions (on or off,
high or low, one or zero, the presence of a signal or absence of a signal). Electronic
circuits designed to work in such a way that only two conditions are possible .
BINARY-CODED - The state in which conditions are expressed by a series of
binary digits (0's and 1's) .
BINARY DIGIT - (1) A character that represents one of the two digits in
the number system that has a radix of two. (2) Either of the digits 0 or 1 that may be
used to represent the binary conditions of on or off .
BINARY NOTATION - See BINARY NUMBER SYSTEM .
BINARY NUMBER SYSTEM - A number system using two digits, symbols, or
characters (usually 1 and 0) .
BINARY POINT - The radix point that separates powers of two and fractional
powers of two in a binary number .
BINDER - A compound consisting of organic resins used to bond the oxide
particles to the base material, the actual composition being considered proprietary
information by each magnetic tape manufacturer. The binder is required to be flexible but
still maintain the ability to resist flaking or shedding during extended wear passes.
BISTABLE - A device that is capable of assuming either one of two stable
states .
BISTABLE MULTIVIBRATOR - A multivibrator that has two stable states. It
remains in one of the states until a trigger is applied. It then flips to the other stable
state and remains there until another trigger is applied. Also referred to as a FLIP-FLOP
.
BIT - An abbreviation for binary digit; the smallest unit of data, either
a 0 or 1.
BIT DENSITY - (See packing density.) bit error rate (BER). - (1) The
number of errors a specific magnetic tape may contain, as used in high-density recording.
(2) Is expressed in errors per data bit, such as 1 in 106, or one error in one million
data bits.
BLACK - The reference color of equipment that passes unclassified
information. It normally refers to patch panels .
BLEEDER CURRENT - The current through a bleeder resistor. In a voltage
divider, bleeder current is usually determined by the 10 percent rule of thumb .
BLEEDER RESISTOR - A resistor used to draw a fixed current .
BLIP - See PIP .
BLOCK DIAGRAM - A diagram in which the major components of an equipment or
a system are represented by squares, rectangles, or other geometric figures, and the
normal order of progression of a signal or current flow is represented by lines .
BLOCKED-GRID KEYING - A method of keying in which the bias is varied to
turn plate current on and off .
BLOCKED RECORDS - One or more logical records grouped and treated as a
unit (physical record or block) for input/output processing.
BLOCKING - A condition in an amplifier, caused by overdriving one or more
stages, in which the amplifier is insensitive to small signals immediately after reception
of a large signal .
BLOCKING FACTOR - The number of records stored in a record block.
BOLOMETER - A loading device that undergoes changes in resistance as
changes in dissipated power occur .
BONDING WIRES - Fine wires connecting the bonding pads of the chip to the
external leads of the package .
BOOLEAN - (1) Pertaining to the process used in the algebra formulated by
George Boole. (2) Pertaining to the operations of formal logic .
BOOLEAN ALGEBRA - A system of logic dealing with on-off circuit elements
associated by such operators as the AND, OR, NAND, NOR, and NOT functions .
BOOLEAN LOGIC - See BOOLEAN ALGEBRA .
BOOT OR BOOTSTRAP - (1) A set of instructions that causes additional
instructions to be loaded until the complete computer program is in storage. (2) A
technique or device designed to bring itself into a desired state by means of its own
action; e.g., a machine routine whose first few instructions are sufficient to bring the
rest of itself into the computer from an input device. (3) That part of a computer program
used to establish another version of the computer program.
BOUNDARY CONDITIONS - The two conditions that the E-field and H-field
within a waveguide must meet before energy will travel down the waveguide. The E-field
must be perpendicular to the walls and the H-field must be in closed loops, parallel to
the walls, and perpendicular to the E-field .
BRANCH - An individual current path in a parallel circuit .
BREAK - In a switch, the number of breaks refers to the number of points
at which the switch opens the circuit; for example, single break and double break .
BREAKDOWN - The phenomenon occurring in a reverse-biased semiconductor
diode. The start of the phenomenon is observed as a transition from a high dynamic
resistance to one of substantially lower dynamic resistance. This is done to boost the
reverse current .
BREAK ELONGATION - The relative elongation of a specimen of magnetic tape
of base film at the instant of breaking when it has been stretched at a given rate.
BRIGHTNESS CONTROL - The name given to the potentiometer used to vary the
potential applied to the control grid of a CRT .
BROADSIDE ARRAY - An array in which the direction of maximum radiation is
perpendicular to the plane containing the elements .
BROWN STAIN - (1) A thin discoloration of the head's top surface, usually
a chemical reaction between the head's surface materials and the tape binder, the tape
lubricant, or the head's bonding materials. (2) Its origin is not well understood, but is
known to occur in low humidity.
BRUSHES - Sliding contacts, usually carbon, that make electrical
connection to the rotating part of a motor or generator .
BUCKLING - (1) A deformation of the circular form of a tape pack. (2)
Caused perhaps by a combination of improper winding tension, adverse storage conditions,
and/or poor reel hub configuration.
BUFFER - A voltage amplifier used between the oscillator and power
amplifier .
BUFFER AMPLIFIER - An amplifier that isolates one circuit from another. It
decreases the loading effect on an oscillator by reducing the interaction between the load
and the oscillator .
BUG - A mistake in a program.
BUILD-UP - (1) A snowballing effect started by debris and tape magnetic
particles embedded in the contamination. (2) The thickness of this build-up can cause an
intense in head-to-tape separation, as well as an increase in the coefficient of friction.
(3) Solvent cleaning of the head's top surface will usually remove the build-up.
BUILT-IN TEST EQUIPMENT (BITE) - A permanently mounted device that is used
expressly for testing an equipment or system .
BULK-ERASED NOISE - See noise.
BULK ERASER (DEGAUSSER) - An equipment for erasing a full reel of
previously recorded signals on tape.
BUNCHER CAVITY - The input resonant cavity in a conventional klystron
oscillator .
BUNCHER GRID - In a velocity-modulated tube, the grid that concentrates
the electrons in the electron beam into bunches .
BURNISHING TOOL - A tool used to clean and polish contacts on a relay .
BUS BAR - A heavy copper strap or bar used to connect several circuits
together when a large current-carrying capacity is required .
BYPASS CAPACITOR - A capacitor used to transfer unwanted signals out of a
circuit; for example, coupling an unwanted signal to ground. Also called a DECOUPLING
CAPACITOR .
BYTE - A group of bits next to each other that is considered a unit; for
example an 8-bit byte.
