1. The average time interval between a storage peripheral (usually a disk
drive or semiconductor memory) receiving a request to read or write a
certain location and returning the value read or completing the write.
measurement of time in nanoseconds (ns) used to indicate the speed of
memory. Access time is a cycle that begins the moment the CPU sends a
request to memory and ends the moment the CPU receives the data it
requested. Memory modules complete this process in as fast as 6ns for PC-133
MHz memory, while older modules can take up to 80ns or more.
Also called 'Ambyx Oven.' A burn-in and test system, developed by Micron,
that performs burn-in and many functional tests under high-stress conditions
to ensure long-term quality and reliability of parts.
A machine that measures critical dimensions of designated areas on the die
at different process levels through the use of a SEM (Scanning Electron
Application specific processor
Highly integrated logic chip designed for specific applications to work
alongside a microprocessor (e.g., a math co-processor, graphics processor,
artificial intelligence processor, LAN processor, digital signal processor).
These chips offload some of the specialized number crunching from the MPU.
The area of the RAM that stores the bits. The array consists of rows and
columns, with a cell at each intersection that can store a bit. The large
rectangular section in the center of the die where the memory is stored.
(American Standard Code for Information Interchange) A method of encoding
text as binary values. The ASCII system requires nearly 256 combinations of
8-bit binary numbers to support every possible keystroke from the keyboard.
A process in a multitasking system whose execution can proceed
independently, "in the background.
Describes a type of L2 cache that is not in synch with the system clock.
Asynchronous cache is slower than its synchronous counterpart, but is
capable of delivering information to the CPU at a rate 10 percent faster
than standard DRAM. Asynchronous cache was first used to boost memory
performance in 386 systems and is still widely used today.
A Synchronous DRAM feature that allows the memory chip's circuitry to close
a page automatically at the end of a burst.
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The capacity to move data on an electronic line such as a bus or a channel.
In short, the amount of data moved relative to a specific time frame. It is
expressed in bits, bytes, or Hertz (cycles) per second. Essentially, a
measure of the capacity of data that can be moved between two points in a
given period of time.
A slot or group of slots that must be populated with modules of like
capacity and fulfill the data width requirement of the CPU.
A method of diagramming memory configurations. The bank schema system
consists of rows and columns that represent memory sockets on a system: rows
indicate independent sockets and columns represent banks of sockets.
A printed circuit board (PCB) that does not have any components on it.
Burst EDO - A variant on EDO DRAM in which read or write cycles are batched
in bursts of four. Burst EDO bus speeds will range from 40MHz to 66MHz, well
above the 33MHz bus speeds that can be accomplished using Fast Page Mode or
Ball Grid Array - a square package with solder balls on the underside for
mounting. Use of BGA allows die package size to be reduced by allowing more
surface area for attachment. Smaller packaging allows more components to be
mounted on a module making greater densities available. The smaller package
improves heat dissipation improving performance. See CSP and FBGA.
A method of encoding numbers as a series of bits. The binary number system,
also referred to as base 2, uses combinations of only two digits - 1 and 0.
Basic Input Output System - often referred to as CMOS, the BIOS provides an
interface for a computer's hardware and software. The BIOS configuration
determines how your hardware is accessed.
Short for Binary Digit, the smallest unit of data that can be processed or
stored by a computer. A bit can have a value of either 1 or 0. Bits make up
'computer' language the same way letters of an alphabet make up human
languages. Different combinations of different bits form 'words' and
'sentences' (actually signals) that a computer understands. Before these
words and sentences can be transmitted from the CPU to memory, or vice
versa, they must be broken down into 8-bit segments called bytes. Older
computers were designed to handle only 8-bit data segments, while newer
models have progressed to 64-bit segments. This larger bit width capacity
generally means better and faster computer performance.
A physical unit of information in a logical record; block size is usually
expressed in bytes.
A circuit or system drawing concerned with major functions and
interconnections between functions.
Square metallic pads on the die where the ball bond is attached. The bond
pad is used to find acceptable eye points.
This is when there is so much memory the chipset needs assistance to deal
with the large loading introduced by the large amounts of memory. A buffer
isolates the memory from the controller to minimize the load the chipset
sees. This means adding logic, particularly drivers, to a SIMM or DIMM to
increase the output current. Buffering is used to overcome signal
attenuation due to capacitive loading. Modules that are "buffered" usually
have small buffer chips mounted on them.
The process of exercising an integrated circuit at elevated voltage and
temperature. This process accelerates failure normally seen as "infant
mortality" in a chip. (Those chips that would fail early during actual usage
will fail during burn-in. Those that pass have a life expectancy much
greater than that required for normal usage.)
Bursting is a rapid data-transfer technique that automatically generates a
block of data (a series of consecutive addresses) every time the processor
requests a single address. The assumption is that the next data-address the
processor will request will be sequential to the previous one. Bursting can
be applied both to read operations (from memory) and write operations (to
The central communication avenue in a PCs system board. It normally consists
of a set of parallel wires or signal traces that connect the CPU, the
memory, all input/output devices, and peripherals and allows data to be
transferred from one system component to another. Busses come in a variety
of bit widths and speeds. To prevent data bottlenecks, the components
attached to a bus must operate at close to the same speed as the bus.
A single transaction occurring between the system memory and the CPU.
A unit of information made up of 8 bits. The byte is the fundamental unit of
computer processing; almost all aspects of a computer's performance and
specifications are measured in bytes or multiples of bytes such as kilobytes
(~1,000 bytes) or megabytes (~1 million bytes), or gigabytes (~ 1 billion
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A small fast area memory holding recently accessed data, designed to speed
up subsequent access to the same data. Typically used between a processor
and main memory.
The circuit in control of the interface between the CPU, cache and DRAM
Cache RAM is high-speed memory (usually SRAM) which is dedicated to storing
frequently requested data. If the CPU needs data, it will check in the
high-speed cache memory first before looking in the slower main memory.
Cache memory may be three to five times faster than system DRAM. Most
computers have two separate memory caches; L1 cache, located on the CPU, and
L2 cache, located between the CPU and DRAM. L1 cache is faster than L2, and
is the first place the CPU looks for its data. If data is not found in L1
cache, the search continues with the L2 cache, and then on to DRAM.
The property of a circuit element that allows it store an electrical charge.
A type of memory typically used in laptop and notebook computers. Credit
card memory features a small for factor and is named for its similarity to
the size of credit card.
(Column Address Select/or Strobe)--A control pin on a DRAM used to and
activate a column address. The column selected on a DRAM is determined by
the data present at the address pins when CAS becomes active.
CAS-RAS (CBR) (CAS before RAS)
CAS before RAS. Column Address Strobe Before Row Address Strobe. A fast
refresh technique in which the DRAM keeps track of the next row it needs to
refresh, thus simplifying what a system would have to do to refresh the
When a device that was initially good now fails to function under any
Extra data bits provided by a DRAM module to support ECC function. For a
4-byte bus, 7 or 8 check bits are needed to implement ECC, resulting in a
total bus width of 39 or 40 bits. On an 8-byte bus, 8 additional bits are
required, resulting in a bus width of 72 bits.
A detail test pattern designed to exercise each individual cell in the
memory and find possible shorts between adjacent columns and data buses
Complementary High-density Metal Oxide Semiconductor.
Complex Instruction Set Computing. This design logic is usually associated
with microprocessors. CISC chips use instructions, or commands, that involve
several steps in one.
The number of pulses emitted from a computer's clock in one second; it
determines the rate at which logical or arithmetic gating is performed in a
synchronous computer. An electrical current that alternates between high and
low voltages. The speed of the clock is measured in Megahertz (MHz).
at which a computer's internal system clock operates. The clock is used to
synchronize operations between the components within the clock.
Complementary Metal Oxide Semiconductor. A process that uses both N- and
P-channel devices in a complimentary fashion to achieve small geometries and
low power consumption. On a PC CMOS generally refers to the BIOS information
stored on a CMOS chip.
Cache On A Stick. Coast modules were used to upgrade a motherboard's L2
cache and Tag memory on some socket 7 and older motherboards.
Chip On Board. A system in which semiconductor dice are mounted directly on
a PC board and connected with bonded wires or solder bumps. The dice are
usually mechanically protected with epoxy.
Part of the memory array. A bit can be stored where a column and a row
Compact Flash Memory
A fast, postage stamp size RAM that is removable. The CF Card weighs half an
ounce, with roughly one-fourth the volume and one-half the thickness of a
PCMCIA Type II Card. The CF Card fits into a CF PC Card Adapter making it
compatible with a standard PCMCIA Type II slot on any notebook or desktop
computer. This allows the easy transfer of stored digital information from
the CF Card to a computer or printer. Currently, the most readily available
application for the CompactFlash Card is the digital still camera.
One of the major units in a computer that interprets and carries out the
instructions in a program.
With respect to semi-conductor packages, the condition of leads in a package
having all elements, or all elements in a seating plane, between two
(Central Processing Unit)--The chip in a computer that has primary
responsibility for interpreting commands and running programs. The CPU is
the most vital component of a computer system. The speed of the CPU has a
significant impact on overall system performance, but the CPU doesn't act
alone. If slower memory is paired with a fast processor, the processor will
be forced to wait for the memory to respond. When the speed mismatch is
extreme, the user will see numerous memory errors and even complete system
Continuity RIMMs are used to fill all unused RIMM sockets in a system.
CRIMMs do not use any active components, and are used to continue the
channel so that the signal can be properly terminated at the motherboard.
Chip Scale Package. CSP is a type of BGA in which the package is roughly the
size of the die. CSP is also known as mBGA or micro-BGA.
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In resonant circuits, the decay of oscillations due to the resistance in the
The signal line that carries the data read from the RAM (Random Access
A marking on all PCB and DRAM components indicating the manufacturing date
of the product.
(Double Data Rate) or SDRAM II--The next generation of the current SDRAM.
DDR finds its foundations on the same design core of SDRAM, yet adds
advances to enhance its speed capabilities. As a result, DDR allows data to
be sent on both the rising and falling edges of clock cycles in a data
burst, delivering twice the bandwidth of standard SDRAMS. DDR essentially
doubles the memory speed from SDRAMs without increasing the clock frequency.
An individual rectangular pattern on a wafer that contains circuitry to
perform a specific function. The internal circuitry is made of thousands of
tiny electronic parts. 'Die' refers to a semiconductor component or part
that has not yet been packaged (also known as 'IC' (Integrated Circuit) or
The bondhead tool on the machine that picks up the die from the precisor and
places it on the leadframe.
The physical measurements of the die.
A material that conducts no current when it has voltage applied to it. Two
dielectrics used in semiconductor processing are silicon dioxide and silicon
A layer of deposited oxide used to isolate metal 1 from metal 2 on
double-level metal processes. This must be done in such a way to prevent
hillock formation on level 1.
The intermingling of molecules of two or more substances. When high
temperature processes are done in diffusion tubes, the high temperature
accelerates diffusion. Typical diffusion furnace temperature is 950 degrees
Centigrade, or 1742 degrees Fahrenheit.
Dual Inline Memory Module. A printed circuit board with gold or tin/lead
contacts and memory devices. A DIMM is similar to a SIMM, but with this
primary difference: unlike the leads on either side of a SIMM, which are
"tied together" electrically, the leads on either side of a DIMM are
electrically independent, ie actually separate circuits which allows for
wider and faster data transfer.
(Dual In-line Package) A form of DRAM component packaging. DIPs can be
installed either in sockets or permanently soldered into holes extending
into the surface of the printed circuit board. The DIP package was extremely
popular when it was common for memory to be installed directly on a
Data mask signal used by SDRAMs to provide byte masking during write
operations. There is one DQM signal for every 8 bits of data width.
A computer memory address that is included as part of the instruction.
A computer feature that allows peripheral systems to access the memory for
both read and write operations without affecting the state of the computer's
Systems using intelligent input/output controllers and direct - memory -
access control to free the CPU of the details of block transfers.
The introduction of an element that alters the conductivity of a
semiconductor. Adding boron to silicon will create a P-type (more positive)
material, while adding phosphorus or arsenic to silicon will create N-type
(more negative) material.
(Dynamic Random Access Memory) DRAM is the most common type of memory and is
"dynamic" because in order for the memory chip to retain data, it must be
refreshed constantly ( a pulse of current through all of the memory cells
every few milliseconds). If the cell is not refreshed, the data is lost.
DRAM temporarily stores data in a cell composed of a capacitor and a
transistor. Each cell contains a specified number of bits. These cells are
accessed by row addresses and column addresses. (See also RAM and SRAM.)
Rambus DRAM) A totally new RAM architecture, complete with bus mastering
(the Rambus Channel Master) and a new pathway (the Rambus Channel) between
memory devices (the Rambus Channel Slaves). A single Rambus Channel has the
potential to reach 500MBp/s to 800Mb/s in burst mode; a 20-fold increase
A printed circuit board that sends signals from the interface board of the
oven to the DUT board and back to the interface board. Each oven slot has a
corresponding driver board located in the back of the oven.
The process of preparing product for shipment in moisture vapor barrier
bags. This process includes tubed or reeled product and a clay desiccant,
and an HIC (Humidity Indicator Card), vacuum-sealed in a moisture vapor
Device Under Test. It is used interchangeably with UUT (Unit Under Test).
Type of RAM (Random Access Memory). To keep data in the D(ynamic)RAM memory,
this data needs to be 'refreshed' (recharged). The electric charge fades out
of a DRAM like air seeps out of a balloon. Because of this change, it is
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Electrically Erasable PROM.
Electrically Alterable Read-Only Memory.
Error Correction Code. A method used to check the integrity of data stored
in memory . ECC memory improves data integrity by detecting errors in memory
and is more advanced than parity because it can detect both multiple-bit
errors and single-bit errors (parity only detects single-bit errors). ECC is
typically found in high-end PCs and file servers where data integrity is
key. An ECC scheme capability is partially determined by the sophistication
of the "systematic code" employed. The systematic code is like a reference
table that the memory system uses to determine whether or not the memory has
returned the correct data. Every time data is stored in memory, this code is
responsible for the generation of check bits which are stored along with the
data. When the contents of a memory location is referenced, the ECC memory
logic uses the check bit information and the data itself to generate a
series of "syndrome bits". If these syndrome bits are all zeros, then the
data is valid and operation continues. If any bits are ones, then the data
has an error and the ECC memory logic isolates the errors and reports them
in the operating system. In the case of a correctable error, the ECC memory
scheme can detect single and double bit errors and correct single bit
A memory feature that allows for faster back to back accesses.
EDO Parity RAM offers the high performance of EDO memory and has built-in
parity which greatly improves reliability. Ideal for high-end PCs and
entry-level servers, EDO Parity modules are compatible with any system that
accepts a standard 72-pin EDO module and are rapidly becoming the new
standard on high-end systems.
(Extended Data Out) EDO RAM is similar to FPM memory, a form of DRAM
technology that shortens the read cycle between memory and CPU. but provides
improved performance by keeping available data longer in memory. It
eliminates much of the wait time by allowing the processor to access data
during the refresh cycle. In other words, the computer can load data as it
is searching for new information. EDO memory is generally 10 to 20% faster
than FPM memory. A computer must support EDO memory in order to notice an
increase in performance.
(Enhanced Dynamic Random Access Memory)--a form of DRAM that boosts
performance by placing a small complement of static RAM (SRAM) in each DRAM
chip and using the SRAM as a cache. Also known as cached DRAM, or CDRAM.
Electrically Erasable Programmable Logic Device. A CMOS PLD made by using
EEPROM technology. It can be erased and reprogrammed.
Electrically Erasable, Programmable, Read-Only Memory chip. EEPROMs differ
from DRAMs in that the memory stays in even if electrical power is lost.
Also, the memory can be erased and reprogrammed.
Electrostatic discharge (ESD)
The dissipation of electricity. ESD can easily destroy semiconductor
End Of Buffer.
Electrically Erasable, PROgrammable, Read-Only Memory chip. EEPROMs differ
from DRAMs in that the memory stays in even if electrical power is lost.
Also, the memory can be erased and reprogrammed.
(ECC on SIMM) A data-integrity checking technology designed by IBM that
features ECC data-integrity checking built onto a SIMM.
Erasable Programmable Read Only Memory
The process of applying a cured-plastic protective housing to components. A
mold compound. An Assembly step.
A process using a chemical bath (wet etch) or a plasma (dry etch) that
removes unwanted substances from the wafer surface.
A local area network allowing several computers to transfer data on a
Even parity and odd parity are two different parity protocols used to check
the integrity of data stored in memory. A memory manufacturer can use either
protocol in a memory product. Even parity adds an additional bit to every
byte of data to make the total number of 1's in the segment even. When the
byte passes to the CPU, the parity circuit checks the byte to be sure it is
still even. If it is, the data is considered to be valid and the parity bit
is removed from the byte. If instead it registers as odd, it is considered
to be invalid and a parity error is generated.
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Description of the rate at which parts fail, usually expressed as percent
Unlike odd and even parity, fake parity is not capable of detecting an
invalid data bit. It was designed to artificially 'satisfy' a parity-enabled
computer without actually checking the data for errors. Fake parity attaches
a bit to each byte of data just like odd and even parity protocols. The
difference is that fake parity simply adds the correct parity bit as the
data is sent to the CPU instead of attaching it before the data is stored to
memory, and recalculating it before the byte passes to the CPU.
Material that fails various tests within the component manufacturing
Fine BGA is a ball grid array package with a fine pitch ball arrangement on
the underside of the package (larger than CSP).
Failures In Time.
Front Side Bus is the data channel connecting the processor, chipset, DRAM,
and AGP socket. FSB is described in terms of its width in bits and it's
speed in MHz.
In computing: A status bit that causes some indication of the state or
condition of the processing unit.
Flash memory is a non-volatile memory device that retains its data when the
power is removed. The device is similar to EPROM with the exception that it
can be electrically erased, whereas an EPROM must be exposed to ultra-violet
light to erase. Flash memory does not need a constant power supply to retain
its data and it offers extremely fast access times, low power consumption,
and relative immunity to severe shock or vibration. These qualities combined
with its compact size, make it perfect for portable devices like scanners
digital cameras, cell phones, pagers, hand-helds and printers. Flash chips
have a lifespan limited to 100,000 write cycles, which means flash will
never replace main memory in computers.
A Teflon Polyurethane wafer holder used to transport individual wafers.
Flatpacks can be stacked to carry and protect several wafers at a time.
A flat, rectangular IC package type with leads sticking out from the sides
of the package.
A circuit with two stable states that can be changed from one to the other.
Flip-flops are the storage element in most of the SRAMs.
Pertaining to the condition of a device or circuit that is neither grounded
nor connected to any potential. (Potential is voltage course or current
In Silicon Gate MOS technology: a gate that is not directly connected to the
rest of the circuit. Used in EEPROMs.
Fast Page Mode - A common DRAM data-access scheme. Accessing DRAM is similar
to finding information in a book. First, you turn to a particular page, then
you select information from the page. Fast-page mode enables the CPU to
access new data in half the normal access time, as long as it is on the same
page as the previous request. This feature is used to support faster
sequential access to DRAM by allowing any number of accesses to the
currently open row to be made after supplying the row address just once.
A device or system that can change the frequency of an alternating current,
whether or not it changes the voltage or phase.
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Approximately 1 billion bits: 1 bit x 1,024 (that is, 1,073,741,824 bits) Or
exactly 2^30 bits.
A unit of measurement approximately equal to 1024 megabytes. Computer
components process data in bytes or multiples of bytes such as kilobytes
(~1,000 bytes), megabytes (~1 million bytes), and gigabytes (~ 1 billion
The wire used to make a physical connection from the device to the
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Die that fail functionality testing. These failures have a visual defect 99
percent time, such as poly or metal bridging, missing geometries or layers,
particles or contaminates.
A structure, attached to or part of a semiconductor device that serves the
purpose of dissipating heat to the surrounding environment; usually
metallic. Some packages serve as heat sinks.
Hyper Page Mode also known as EDO.
High Temperature Operating Life.
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Connection to a CPU that is configured or programmed to provide data path
between the CPU and external devices such as a keyboard, display, or reader;
it may be an input port or an output port, or it may be bi-directional.
Integrated Circuit. A tiny complex of electronic components and their
connections that is produced in or on a small slice of material (as
In Circuit Emulator.
Identification Detect. Pins present on DIMMs to provide information to the
system using the module.
Standard set by IEEE (Institute of Electrical and Electronics Engineers) for
communication between pieces of electronic apparatus.
Used to describe the occurrence of premature failures at a higher than
A burn-in process whereby electrical functionality of the parts is
continuously or periodically monitored and recorded under various voltages,
temperatures, and refresh conditions during the burn-in process. This
continuous or periodic monitoring of the functionality of each IC allows
intelligent decisions to be made.
A PCB that interfaces between the computer and an interface board.
Current x Resistance = Voltage. Also an abbreviation for Infrared.
An amorphous, doped polysilicon used as an underlying layer for the HSG poly
to increase conductivity.
International Standards Organization.
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Electron Device Engineering Council - the group that establishes the
industry standards for memory operation, features and packaging.
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Notches on a memory module that prevent it from being installed incorrectly
or into an incompatible system.
Kilobit Approximately one thousand bits: 1 bit x 210 (that is, 1,024
A unit of measurement approximately equal to 1024 bytes. Computer components
process data in bytes or multiples of bytes such as kilobytes (~1,000
bytes), megabytes (~1 million bytes), and gigabytes (~ 1 billion bytes).
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Level 1 cache. A small cache integrated in processor that provides a small
working space for quick access to the most recently used data.
A specialized memory unit that enhances DRAM performance by providing the
CPU with data at speeds ten times faster than DRAM. The L2 cache is
comprised of Static RAM (SRAM), a high-speed RAM that does not need to be
refreshed to retain its data. Most computers have two different memory
caches; L1 cache, located on the CPU, and L2 cache, located between the CPU
and DRAM. L1 cache is faster than L2, and is the first place the CPU looks
for its data. If data is not found in L1 cache, the search continues to the
L2 cache and then to DRAM. In early processors, the L2 cache was not
integrated into the processor but rather built into the motherboard, and was
in some cases upgradeable. See COAST.
Process which uses a YAG (Yittrium-aluminum-Garnet) laser to melt the
silicon in a dot matrix to form wafer scribe numbers.
Circuit element that stores a given value on its output until told to store
a different value.
An undesired phenomenon in an integrated circuit whereby a circuit locks in
a certain state and will not change.
The effective input voltage at which a flip-flop changes states.
The metal extensions from an IC package or discrete component that connects
the component to the PCB. The leg or contact point of the component that is
either physically soldered to a PC board or placed within a socket for
A metal structure that is part of the device. The die is attached to the
Leads or Legs: The official name for the metal 'feet' on an IC. Also called
'pins.' The part of the lead assembly that is formed after a portion of the
lead frame is cut away. The part's connection to the outside world.
Undesirable conductive paths in components, subsystems, and systems; also
the current through such paths.
Accelerated testing of electronic components to establish their field
A circuit that produces a voltage output approximately proportional to the
input voltage, generally over a limited range of voltage frequency.
Power supply design in which the voltage is held constant by dissipating 50%
of the input voltage times and output current as a margin.
A method of selecting memory or input/output devices that dedicates one
address line per chip selection; results in overlapping or noncontiguous
memory; used because it is the cheapest method of selection.
A pin in the mold which locates the leadframe in the correct position on the
mold for processing.
An integrated circuit which provides a fixed set of output signals according
to the signals present at the input.
Several individual device functions on an integrated circuit chip.
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Detail test pattern designed to check for decoder and cell interaction
Amount of memory equal to 1 bit x 1,0242 or 1,048,576 bits of information.
Amount of memory equal to 1,048,576 bytes of information. (Abbreviated MB.)
A Term commonly used to refer to computer system's random access memory (see
also RAM). The term memory has also been used to refer to all types of
electronic data storage (see storage). A computer system's memory is crucial
to its operation; without memory, a computer could not read programs or
retain data. Memory stores data electronically in memory cells contained in
chips. The two most common types of memory chips are DRAM and SRAM.
A logical unit of memory in a computer, the size of which is determined by
the computer's CPU. For example, a 32-bit CPU calls for memory banks that
provide 32 bits of information at a time.
The amount of memory in an IC and how it is accessed. Also, a code on the
lot traveler used to indicate the IC's memory configuration (e.g., 1M1 = 1
Meg x 1, 4M4 = 4 Meg x 4, etc.).
The logic chip used to handle the I/O (input/output) of data going to and
from memory. See chipset.
Minimum amount of time required for a memory to complete a cycle such as
read, write, read/write, or read/modify/write.
Data SRAM: quick-access chip.
dynamic random access memory.
synchronous dynamic random access memory.
SDRAM double data rate dynamic random access memory.
SLDRAM synchronous link dynamic random access memory.
(also DRDRAM) Rambus dynamic random access memory.
EPROM: erasable, programmable, read-only memory.
programmable, read-only memory.
random access memory.
read-only memory (permanent memory that cannot be changed).
static random access memory.
Megahertz is a measurement of clock cycles in millions of cycles per second.
A unit of measure equivalent to one-millionth of a meter; synonymous with
Millions of Instructions Per Second. This measurement is generally used when
describing the speed of computer systems.
Metal Nitride Oxide Semiconductor. The technology used for EAROMs
(Electrically Alterable ROMs); not to be confused with NMOS.
Moisture vapor barrier bag
A vacuum-sealed bag designed to keep the moisture out so that the parts
inside will not be damaged.
Contained on one chip or substrate, as a microprocessor system including not
only the logic but also memory or input/output circuits.
Metal-Oxide-Semiconductor. Layers used to create a semiconductor circuit. A
thin insulating layer of oxide is deposited on the surface of the wafer.
Then a highly conductive layer of tungsten silicide is placed over the top
of the oxide dielectric.
Device in which current flow occurs in a single channel of P- or N-type
material and is controlled by an insulated electrode on the surface of the
The set of chemical and metallurgical steps used to make MOS Large Scale
Metal Oxide Semiconductor Transistor.
Motherboard (also known as Mainboard)
Also known as logic board, main board, or system board; your computer's main
electronics board, which in most cases either contains all CPU, memory, and
I/0 functions, or has expansion slots that support them.
Mean Time Between Failures.
Mean Time To Failure.
Memory Unit. Usually a printed circuit board assembly populated with memory
chips that stores a certain quantity of memory. Intel term for one of the
types of cards in a memory system card set.
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A computer logic circuit that produces an output which is the inverse of
that of an AND circuit.
Literal: One-billionth (10 to the -9). Diffusion: A tool used to measure the
thickness of a film on a wafer.
One billionth of a meter.
One billionth of a second. Memory data access times are measured in
nanoseconds. For example, memory access times for typical 30- and 72-pin
SIMM modules range from 60 to 100 nanoseconds.
Charge caused by the presence of electrons, not their absence.
A unit of force in the meter-kilogram-second system needed to accelerate a
mass of one kilogram one meter per second per second.
Usually 4 bits or half a byte.
N-channel Metal Oxide Semiconductor. This pertains to MOS devices
constructed on a P-type substrate in which electrons flow between N-type
source and drain contacts. NMOS devices are typically two to three times
faster than PMOS devices.
A term created by Apple Computer, Inc. that describes a memory module which
uses 16-Mbit technology. For a given capacity, a noncomposite module will
have fewer chips than a composite module.
Types of memory that retain their contents when power is turned off. ROMs,
PROMs, EPROMs and flash memory are examples. Sometimes the term refers to
memory that is inherently volatile, but maintains its content because it is
connected to a battery at all times, such as CMOS memory and to storage
systems, such as hard disks.
Nanosecond (ns). One billionth of a second; used to measure the speed of the
parts (e.g., -07 nanoseconds).
Non-Volatile Random Access Memory.
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Even parity and odd parity are two different parity protocols used to check
the integrity of data stored in memory. A memory manufacturer can use either
protocol in a memory product. Odd parity adds an additional bit to every
byte of data to make the total number of 1s odd. When the byte passes to the
CPU, the parity circuit checks the byte to be sure it is still odd. If it
is, the data is considered to be valid and the parity bit is stripped from
the byte. If instead it registers as even, it is considered to be invalid
and a parity error is generated.
Output-Enable. On a part, where data-in and data-out are shared on the same
pins, the OE must be triggered to request output data.
A unit of measure of electrical resistance.
A circuit interruption that results in an incomplete path for the current
flow. (e.g., an open wire which opens the path of the current).
Software controlling the overall operation of a multipurpose computer
system, including such tasks as memory allocation, input and output
distribution, interrupt processing, and job scheduling.
An electronic circuit which amplifies 'linear' (also called analog) signals.
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A conductive bonding island located strategically on circuit chips for
inter-connecting circuit elements or for bringing connections from circuit
leads to the outside.
The number of bits that can be accessed from one row address.
Mode in which if RAS is kept low and the DRAM is given a column-address
without being given a new row-address, the chip will remember which row it
was on the last time and automatically stay on that row. It is like saying
that all the bits along one row are all on the same 'page,' and the part
will assume the same page is intended until a different page is specified.
Programmable Array Logic. A device that can be programmed to do certain
logic functions. Then a fuse inside of the device can be blown so the
programmed information can never be changed. Sometimes called a PLD
(Programmable Logic Device) Language.
A test of the DUT that checks for pin leakage, the amount of current it
draws, opens, and shorts.
A test that measures values, also called a dynamic test as opposed to a
functional or Go/No-Go test.
A series of voltage and current tests performed on all products in Probe.
The test checks for variations in the fabrication process. Test results are
used by engineers to modify or correct processes.
A quality control method that checks the integrity of data stored in a
computer's memory. Parity works by adding an extra bit of data to each byte
to make the total number of 1's either odd or even An error is detected if
the parity circuit determines that this number has changed, indicating that
some of the data may have been lost or otherwise corrupted. Two different
parity protocols exist, even parity and odd parity. Parity protocols are
capable of detecting single bit errors only. To enable multiple-bit error
detection, manufacturers must use a more advanced form of error checking
called Error Correcting Code (ECC). See also Fake Parity.
A bit added to a group of bits to detect the presence of an error.
The portion of a language translator (compiler or assembler) which
determines the logical structure of the program being completed.
A device incapable of current gain or switching such as a resistor or
A circuit element without an energy source such as a capacitor or resistor.
Intel's PC100 specification defines the requirements for SDRAM used on 100
MHz FSB motherboards. Around the middle of 1998, Intel introduced the BX
chip set to their motherboard designs. One element in this new architecture
will include an increase in the PC main memory bus speed (Host bus) from 66
to 100 MHz, called PC 100. To match the 100MHz bus speed, 100MHz SDRAM
modules is the required memory technology for this new chip set.
The PC133 specification details the requirements for SDRAM used on 133MHz
FSB motherboards. PC133 SDRAM can be used on 100MHz FSB motherboards but
will not yield a performance advantage over PC100 memory at 100MHz.
(Printed Circuit Board) A component made up of layers of copper and
fiberglass; the surface of a PCB features a pattern of copper lines, or
"traces," that provide electrical connections for chips and other components
that mount on the surface of the PCB. Examples: motherboard, SIMM, credit
card memory, and so on.
(Personal Computer Memory Card International Association) A standard that
allows interchangeability of various computing components on the same
connector. The PCMCIA standard is designed to support input/ output devices,
including memory, fax/modem, SCSI, and networking products.
Presence Detect. Indicator pins on SIMMs and DIMMs that provide information
to the system using the module.
Pin Grid Array.
The metal extensions from an IC package or discrete component that connects
the component to the PCB.
The hole located on the 'pin one' side of the leadframe.
An indentation or mark on the top of the part that indicates where the first
lead of the die inside is located.
Pipeline Burst Cache
A type of synchronous cache that uses two techniques to minimise processor
wait states - a burst mode that pre-fetches memory contents before they are
requested, and pipelining so that one memory value can be accessed in the
cache at the same time that another memory value is accessed in DRAM.
Programmable Logic Array. An array of logic elements that can be programmed
to perform a specific logic function. It can be as simple as a gate or as
complex as a ROM and can be programmed (often by mask programming) so that a
given input combination produces a known output function.
Programmable Logic Devices. Devices with 10-100 times higher level of
integration than a TTL; called programmable because they can be customized
in software rather than in hardware.
P-channel Metal Oxide Semiconductor. This pertains to MOS devices
constructed on an N-type silicon substrate in which holes flow between
source and drain contacts.
Protective covering over the die; also called Die Coat
Poly-crystalline layer of silicon used for the silicon gate contact in
silicon gate MOS devices; also used for interconnections between devices.
A PCB with components.
To turn the system's power OFF.
To turn the system's power ON.
Plastic Quad Flat Pack. A square, flat package with gullwing leads located
around all four sides of the package.
Cache that is closest to the processor: typically located inside the CPU
chip. Can be implemented either as a unified cache or as separate sections
for instructions and data. Also referred to as Level 1 cache or internal
Wire used to make electrical contact with a pad on a die; usually made of
either beryllium copper, tungsten, or palladium. The diameter of the probe
shank is 10 mils, the diameter of the standard probe tip is 1.5 mils, and
the length is 7 or 14 mils.
A fiberglass card (P.C. Board) that has a hole in the center in which there
are pins that are aligned and placed on pads located on the die. As the pins
on the probe card are placed on die pads, the probe card tests and sorts die
Memory that is custom-designed for a specific computer.
A device or method used to keep the output voltage of a device at a high
level; often a resistor network connected to a positive supply voltage.
Printed Wiring Board; board upon which there are layers of printed circuits
where DRAMs can be attached with solder so that memory can be accessed.
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QFP: A flat, rectangular, integrated circuit with its leads projecting from
all four sides of the package without radius.
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Random Access Memory - A type of memory that can be written to and read from
in a nonlinear (random) manner. When an application is opened. it is
transferred from the hard drive to RAM where it is more readily accessible.
RAM enhances system performance because it can process requests from the CPU
more quickly than the hard drive. The kind of RAM used in main memory on
most computers is Dynamic RAM (DRAM). DRAM stores data as electronic
signals. These signals must be constantly refreshed to keep them from
dissipating. The more RAM your computer has, the more data it can store at
one time and subsequently the more efficiently your computer will operate.
The data held in RAM is lost when the computer is turned off. The term
random derives from the fact that the CPU can retrieve data from any
individual location, or address, within RAM.
A period of time in the oven when the temperature goes up.
The portion of the bathtub curve that represents the useful portion of
The difference between the smallest and largest values in a set of data.
This is the simplest measure of variation.
Row-Address-Strobe: the signal that tells the DRAM to accept the given
address as a row-address. Used with CAS and a column-address to select a bit
within the DRAM.
Rambus DRAM is an evolutionary type of DRAM that uses a 16-18 bit data path
and is designed to operate with FSB speed of 800 MHz producing a burst
transfer rate of 1.6 gigahertz. Rambus DRAM technology is a system-wide,
chip-to-chip interface design that allows data to pass through a simplified
bus. Rambus uses a unique RSL (Rambus Signaling Logic) technology. Rambus is
available in two flavors: RDRAM and Concurrent RDRAM. The third line
extension, Direct RDRAM, was developed in stages and went into production in
1999. In late 1996, Rambus agreed to a development and license contract with
Intel that lead to Intel's i820 and i840 chip sets supporting Rambus memory
being released in 1999.
The amount of time required for the output data to become valid once the
read and address inputs have been enabled; generally called access time.
A mode of operation used in core memory systems.
A generic term for Random Access Memories.
An electrical process used to maintain data stored in DRAM. The process of
refreshing electrical cells on a DRAM component is similar to that of
recharging batteries. Different DRAM components call for different refresh
This is a count of the number of rows (in thousands) refreshed at a time in
a refresh cycle. Common refresh rates are 1K, 2K, and 4K. DRAM stores data
as a series of electron charges in individual cells. This data must be
constantly recharged or 'refreshed' to keep the data from dissipating. The
refresh rate refers to the size of the data that must be recharged, and is
typically expressed in kilobytes (~1,000 bytes). Two common refresh rates
are 2K and 4K, with 2K being the faster rate.
Registers delay memory information for one clock cycle to ensure all
communication from the chipset is collected by the clock edge, providing a
controlled delay on heavily loaded memories.
An identifier that indicates the position of a memory location in a computer
routine relative to the base address as opposed to the memory location's
The amount of time data must remain stable after a device or circuit has
been clocked; also called 'hold time.'
A material that prevents etching or plating of the area it covers; also
Rambus Inline Memory Modules used for RAMBUS DRAM. A form of chip packaging
that is similar to DIMMs using Direct Rambus DRAM memory subsystems.
Reduced Instruction Set Computing. The design methodology is usually
associated with microprocessors. RISC chips use simpler instructions, or
commands, than CISC chips. However, they need to use more steps to perform
many functions that CISC chips perform in one step. SPARC and MIPS chips are
based on RISC.
The amount of time required for a signal level change to increase from ten
percent to ninety percent of its final specified value.
Returned Material Authorization; required if a customer desires to return
products. Also refers to parts that have been returned from a customer.
Read Only Memory - A form of random access memory that can only be read
from, not written to. Most systems use ROM to store the instructions a
computer needs during the startup process.
Part of the RAM array; a bit can be stored where a column and a row
Describes how many rows are on a wafer map in the X direction. (X = left to
right. Y = top to bottom).
An acronym to represent RS/1 Programming Language. RPLs are functions or
procedures written in RS/1's built in programming language. These RPLs are
used to automate tasks and analyses.
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A marking on a wafer that identifies the wafer and the lot it came from. The
scribe is located on the front of the wafer, opposite the major flat.
Synchronous Dynamic Random-Access Memory. A DRAM technology that uses a
clock to synchronize signal input and output on a memory chip. The clock is
coordinated with the CPU clock so the timing of the memory chips and the
timing of the CPU are "in synch." The synchronization eliminates time delays
and allows for fast consecutive read and write capability, thereby
increasing the overall performance of the computer. SDRAM has two separate
memory banks that operate simultaneously, while one bank prepares for
access, the other is being accessed. SDRAM allows the CPU to access memory
approximately 25 percent faster than EDO memory because it is controlled by
the system clock. SDRAM can only be used in computers designed for it and
cannot be mixed with any other type of memory. SDRAM can operate at 100MHz,
133Mhz and features a burst mode that allows it to address blocks of
information instead of small data bits.
Cache that is second closest to the processor; typically located on the
system board. Also referred to as Level 2 cache and external cache.
A memory technology that enables DRAM to refresh on its own-independent of
the CPU or external refresh circuitry. This technology is built into the
DRAM chip itself and reduces power consumption dramatically. It is commonly
used in notebook and laptop computers.
Soft Error Rate. An error caused by temporary disruption of memory cell.
Presence Detect (SPD)
Serial Presence Detect. An enhanced presence detect that uses an EEPROM to
store modules timings, configuration, and the manufacturer's data.
An element, such as silicon, that has intermediate in electrical
conductivity between conductors and insulators, which conduction takes place
by means of holes and electrons.
The sense amp acts as a distributor of current on the die.
A device or circuit capable of sensing very low voltages and amplifying them
to some higher voltage level.
Syncronous Graphics RAM. A single port DRAM designed for graphics hardware
that require high speed throughput such as 3-D rendering and full-motion
A reduction in die (chip) size. A reduction in the size of the circuit
design resulting in smaller die sizes that increases the number of possible
die per wafer.
Single In-line Module. Same as SIP except with a connector edge instead of
Single In-line Memory Module - a high-density DRAM package alternative
consisting of several components connected to a single printed circuit
board. A small PCB designed to mount in a socket on a larger PCB providing a
large memory upgrade in a small space. This board provides the connection
between multiple memory chips and the computer system. SIMMS come in various
pin configurations, the most common type being: 30 pin and 72 pin. A 30 pin
SIMM has a row of 30 tin or gold pins long the bottom of the module which
determine the amount of data the module can handle. These pins connect to
only one memory chip as opposed to DIMMs which can connect to multiple
An interconnect component mounted on the system board, or motherboard,
designed to hold a single SIMM.
Single In line Package. A component or module that has one row of leads
along one side. Many resistors come in SIP form.
Synchronous Link Dynamic Random Access Memory. SLDRAM is the next evolution
of SDRAM using a multiplexed command bus allowing fewer pins to increase
bandwidth and allow higher FSB speeds.
Small Outline Dual Inline Memory Module. Smaller and thinner than standard
DIMMs, SODIMMs are typically used in laptop computers and mobile computing
devices. An enhanced version of a standard DIMM. The small outline DIMM is
about half the length of a typical 72-pin SIMM. SO DIMMs come in a variety
of pin sizes and can be installed either singly to support 32-bit systems,
or in pairs to support 64-bit systems.
An error caused by a temporary disruption of the memory cell.
A part with a temporary, single-bit failure during the soft error test.
Small Outline Rambus Inline Memory Module. SORIMMs have a smaller profile
that standard RIMMs and are used in laptop computers and systems that have
strict size requirements.
Small Outline J-lead package. A rectangular package with leads sticking out
of the side of the package. The leads are formed in a J-bend profile,
bending underneath and towards the bottom of the package.
Statistical Process Control. The use of statistics to determine uniformity
around a target value.
(Serial Presence Detect)
An enhanced presence detect that uses an EEPROM to store manufacturer data.
The time it takes the RAM to put information into its memory or get
information out of its memory. It is measured from the time that an address
and proper control signals are given, until the information is stored or
placed in the device's output(s).
Our coding for the speed that the stored information in the part can be
retrieved by a computer. For DRAMs, a -5 is 50 nanoseconds, a -6 is 60
nanoseconds, a -7 is 70 nanoseconds, etc. For SRAMs, a -10 is 10
An operation found in coat and develop programs that stands for spin high
The sudden drastic portion of a pulse that significantly exceeds its average
amplitude. Standard deviation A measure of variation for a particular
process or product characteristic. This is often abbreviated as 'STD DEV' or
Standard Readability Assessment.
(Static Random Access Memory) An integrated circuit similar to a DRAM
(Dynamic Random Access Memory) with the exception that the memory does not
need to be refreshed. SRAM is faster and more expensive than DRAM and is
generally used for speed-critical areas of the computer such as cache
Smallest or lowest address that a memory system will respond to.
Unlike volatile memory, static memory retains its contents even when the
main current is turned off. The trickle of electricity from a battery is
enough to refresh it.
A medium designed to hold data, such as Floppy Diskette, Harrd Disk Drive or
An input that allows parallel data to be entered a synchronously.
The actual structural material on which semiconductor devices are
fabricated, whether passive or active. The term applies to any supportive
material, such as the materials used in the fabrication of printed circuits.
A J-leaded or Gullwing package or BGA that can be mounted directly on the
surface of P.C. Boards (as opposed to through-hole packages).
The menu in BIOS containing user-configurable options for a PC's hardware
A kind of L2 cache that is synchronized with the CPU. This eliminates the
lag time created while the CPU waits for cache memory to fulfill its
requests. Synchronous cache is typically 3 to 5 percent faster than
asynchronous cache, and is a full 20 percent faster than standard DRAM. See
also Asynchronous Cache.
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The subset of the CPU address bits used to compare the tag bits of the cache
directory to the main memory address being accessed. Tag memory acts as an
index for the information stored in L2 cache.
Cache is physically divided into two sections. The Tag RAM section stores
the Tag address of the location of the data in cache. This section is
smaller than the Data RAM section, which stores the actual data or
To Be Determined. Used on quotes in reference to shipping dates.
A measurement of the speed or how fast the part is; it is the time it takes
to get a bit of information out of the part after CAS comes down.
Thermal Coefficient of Expansion. A constant that describes the changes in
linear dimensions with respect to temperature for a device or material.
A code for TSOP (see TSOP). A package-type code.
Thin Small Outline Package. It is thinner and slightly smaller than an SOJ
and with gullwing-shaped leads. A thin, rectangular package with leads
sticking out the sides of the package. TSOP DRAM mounts directly on the
surface of the printed circuit board. The advantage of the TSOP package is
that it is one-third the thickness of an SOJ package. TSOP components are
commonly used in small outline DIMM and credit card memory applications.
An electrical process every product goes through which tests the parts for
parametric, speed, and functional failures.
A semiconductor device that uses a stream of charge carriers to produce
active electronic effects.
The process of creating a printed circuit on a printed circuit board (PCB).
This number (x8, x9, x32, x36, x64, x72, x80) refers to the bit depth of a
module, or to the size of the data path used to access the memory.
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This is where the chipset controller deals directly with the memory. There
is nothing between the chipset and the memory as they communicate.
Micron (or micrometer). A unit of length equal to one millionth of a meter.
Microsecond: One millionth of a second.
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Collector Common Voltage.
Memory that loses its contents when the power is turned off. A computer's
main memory, made up of dynamic RAM or static RAM chips, loses its content
immediately upon loss of power. Contrast ROM, which is non-volatile memory.
Video RAM. DRAM with an on-board serial register/serial access memory
designed for video applications. VRAM has two separate data ports. One is
dedicated to updating the image on the screen while the other one is used
for changing the image data stored in memory. This "dual-ported" design
gives higher performance than DRAM which cannot read and write
simultaneously but is more expensive.
Vss is the abbreviation for the ground on a connection. (Like the ground
wire on a battery.)
A condition, transaction, or event that changes or may be changed as a
result of processing additional data through a system.
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Write-Enable; WE must be pulsed low when data is written to the chip.
Time expended from the moment data is entered for storage to the time it is
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An addressing mode in which the address is given as an unsigned binary
number that specifies one of the memory locations between 0 and
A unit of measure expressing the intensity of light
reflected off an object. 1 lambert = 0.318 foot-candles per
LAN - Local Area Network
A local area network is a group of computers and associated
devices that share a common communications line and
typically share the resources of a single processor or
server within a small geographic area (for example, within
an office building).
LCD (Liquid Crystal Display)
Liquid Crystal Display technology is one of the methods used
to create flat-panel TVs. Light isn't created by the liquid
crystals; a light source (bulb) behind the panel shines
light through the display. The display consists of two
polarizing transparent panels and a liquid crystal solution
(liquid containing rod-shaped crystals) sandwiched in
between. An electric current passed through the liquid
causes the crystals to align so that light cannot pass
through them. Each crystal acts like a shutter, either
allowing light to pass through or blocking the light. The
pattern of transparent and dark crystals forms the image.
LCD technology is used in direct-view, rear-projection, and
front-projection TVs, and is fundamentally different from
the CRT technology used in conventional TVs.
Utilizing the LCD technique, these projectors separate the
red, green and blue information to three different LCD
panels. Since LCD panels do not produce color, the
appropriate colored light is then passed through each panel
and combined to exit through the projector lens and onto a
LCOS (Liquid Crystal On Silicon) A projection TV display
LCOS technology is used in rear-projection, and
front-projection TVs. Liquid Crystal on Silicon. This is a
reflective display technology where one glass substrate is
attached to a silicon chip which is coated with crystals.
The chip contains the control circuitry. LD - See Line
A screen surface characterized by silvered or aluminized
embossing, designed to reflect maximum light over wide
horizontal and narrow vertical angles. It must be held very
flat to avoid hot spots. A large series of parallel
lenticulations cut vertically into the screen surface to
improve horizontal dispersion.
A cylindrical lens which causes light passing through it to
be dispersed perpendicular to its axis.
The scaling of a widescreen image to fit a standard 4:3
aspect ratio TV screen by shrinking the image so that the
width fits exactly. The horizontal black bars that appear
above and below the image are actually recorded with the
picture, so some of the picture's vertical resolution is
lost when you view it. Letterboxing is much more common on
DVD movies than VHS videos.
The relative intensity of an audio or video source.
The level control on some interface products is similar to
the contrast control on a data monitor. It can either
increase or decrease the output signal level from the
interface to a data monitor or projector. This results in
greater or less contrast in the picture.
Light emitting diode - LED
A low-power, long life, light source, usually red, green or
yellow in color. Some LEDs can produce two different colors.
The intensity of a given lighting situation as measured in
Measures the amount of light produced by a front projector.
Expressed in "lumens" or "ANSI lumens," with a higher number
indicating greater light output.
An Increased Definition Television (IDTV) feature that
doubles the number of scan lines in a video picture. This
fills the space between the original lines, making them less
noticeable and increases the brightness of the picture. For
example, the NTSC video field of 262.5 lines is doubled to
525 non-interlaced lines and the PAL field of 312.5 lines
Audio signal industry-referenced at 600 ohms, 0dB. Consumer
systems may use a different reference.
Line out - Audio output
In consumer systems, this may be 10,000 -50,000 ohms, at
-10dB or -20dB.
Alternating current (AC) at the level typically found in the
The ability of a display device to produce an object the
same size anywhere on the screen. For example, poor
linearity may show the same line of text one size when it is
at the top of the screen, but a different size when it is at
the bottom of the screen.
More than just a digital audio format, Liquid Audio offers
software for music management and playback (Liquid Player),
and a network of affiliated web sites (Liquid Music Network)
that sell downloadable, copy-protected music. Liquid Audio
files usually appear with the .LQT or .LA1 extension. They
can utilize several different types of compression, and can
come in streaming or downloadable form.
A feature that allows the video signal to be passed through
a device relatively unprocessed and sent to a local monitor
or other device. The loop-through is separate from the
circuits that process a signal for output to the main
presentation or recording device(s). Loop-through
connections are found on some scan converters and scalers.
When using compression to reduce text and/or graphic files,
some techniques "throw away" data in the process. Methods
that compress files without losing data are called
"lossless". Examples include LZW (Lempel-Ziv Welch), PKZIP
or Zip 8-bit.
A term to describe compression techniques that throw away
data as part of the process. The more data "loss", the
smaller the file, and the lower the quality (grainy or
jagged edged) image. Lossy compression methods include JPEG
and MPEG. Note: with JPEG, "high" means high compression
(greater loss) and "low" means low compression (less loss).
The condition where the source or load is at a lower
impedance than the characteristic impedance of the cable.
Low source impedance is common; low load impedance is
usually a fault condition. Example: 30 - 600 ohms.
LNB (Low Noise Blocker)
The amplifier that blocks low-end frequencies and receives
the high-end frequencies used in digital satellite
transmissions. This amplifier is located at the end of the
arm projecting from the satellite dish.
A single-output LNB dish provides one RF output for
connecting an RG-6 coaxial cable to feed the digital signal
to a single satellite receiver. A dual-output LNB dish has
two RF outputs for distributing satellite signals to two or
Luma - Also called Luinance
The photometric radiance of a light source. The luma signal
represents brightness in a video picture. Luma is any value
between black and white and is abbreviated as "Y". Also see
A video problem in which the intensity of an object or area
is shifted slightly to the right of the color. The color
occurs in the correct area of the displayed image, but the
luma (intensity) starts later.
Lumen - LM
The unit of measure for light output of a projector.
Different manufacturers may rate their projectors' light
output differently. "Peak lumens" is measured by
illuminating an area of about 10% of the screen size in the
center of the display. This measurement ignores the
reduction in brightness at the sides and corners of the
The more conservative "ANSI lumens" (American National
Standards Institute) specification is made by dividing the
screen into 9 blocks, taking a reading in the center of
each, and averaging the readings. This number is usually
20-25% lower than the peak lumen measurement. A unit of
measure for the amount of light emitted by a source. 0.98
Ft-c (foot-candles) of light covering a surface of 1 square
The brightness component of a color video signal. Determines
the level of picture detail. See Luma
The amount of light per square meter, incident on a surface.
The term applied to metric measurement of light intensity
taken at the illuminated surface. One foot-candle (FT-c) =
10.76 lux, or 1 lux = 1 lumen/square meter = 0.093
LVDS - Low Voltage Differential Signal
A signal transmission standard developed for the connection
of laptop computers to their local LCD displays. National
Semiconductor is the manufacturer that is promoting this
standard. SGI used LVDS on the 320 and 540 NT Visual
Workstations for connection to their 1600SW series, 16x9
aspect ratio, LCD monitor.
Lempel-Ziv Welch. A lossless method of file compression
Absorption: Reduction of acoustical energy usually by converting it into
heat via friction using soft, fibrous materials.
AC3: Audio Codec 3. This was the original and more
technical name for Dolby Digital. Replaced by marketing mavens when they
realized that Dolby's name was not in the title. Some RF modulated, 5.1-encoded
laser discs were labeled as AC3. Later versions were labeled as Dolby Digital.
Academy Curve: An intentional roll-off in a theatrical
system's playback response above ~2kHz (to -18dB at 8kHz) to minimize noise in
mono optical tracks. Some (many) transfers to home video of mono movies have
neglected to add the Academy filter during transfer, giving many old movies a
screechy sound they were never intended to have. A few home processors have an
Academy filter option, making them a must for old-movie buffs. Has been used
Acoustic Suspension: A sealed speaker enclosure that uses
the air trapped in the cabinet as a reinforcing spring to help control the
motion of the woofer(s).
Active: Powered. An active cross-over is electrically
powered and divides the line-level signal prior to amplification. An active
speaker includes an active crossover and built-in amplifier.
Amplifier: A component that increases the gain or level
of an audio signal.
AM: Amplitude modulated.
Anamorphic: Process that horizontally condenses
(squeezes) a 16:9 image into a 4:3 space, preserving 25 percent more vertical
resolution than letterboxing into the 4:3 space. For the signal to appear with
correct geometry, the display must either horizontally expand or vertically
squish the image. Used on about two or three promotional laser discs and many
DVDs. Also called Enhanced for Widescreen or Enhanced for 16:9.
Aspect Ratio: The ratio of image width to image height.
Common motion-picture ratios are 1.85:1 and 2.35:1. Television screens are
usually 1.33:1 (also known as 4:3), which is similar to the Academy standard for
films in the '50s. HDTV is 1.78:1, or 16:9. When widescreen movies (films with
aspect ratios wider than 1.33:1) are displayed on 1.33:1 televisions, the image
must be letterboxed, anamorphically squeezed, or panned-and-scanned to fit the
ATSC: Advanced Television Systems Committee.
Government-directed committee that developed our digital television transmission
Attenuate: To turn down, reduce, decrease the level of;
the opposite of boost.
A-Weighting: Measurement based roughly on the uneven
frequency sensitivity of the human ear. The influences of low and high
frequencies are reduced in comparison to midrange frequencies because people are
most sensitive to midrange sounds.
Balanced Input: A connection with three conductors: two identical signal
conductors that are 180 degrees out of phase with each other, and one ground.
This type of connection is very resistant to line noise.
Bandpass: A two-part filter that cuts both higher and
lower frequencies around a center band. A bandpass enclosure cuts high
frequencies by acoustic cancellation and low frequencies by natural physical
limitations on bass response.
Bandwidth: In audio, the range of frequencies a device
operates within. In video, the range of frequencies passed from the input to the
Bass: Low frequencies; those below approximately 200 Hz.
Bass Reflex: See Port.
Bipolar: 1) The condition of possessing two pole sets. In
a conventional (non-FET) transistor, one pole set exists between the base and
collector, and the other pole set exists between the base and emitter. 2)
Speakers that consist of two driver arrays facing opposite directions and wired
in electrical phase with one another to create a more diffuse soundstage.
Bi-Wiring: A method of connecting an amplifier or
receiver to a speaker in which separate wires are run between the amp and the
woofer and the amp and the tweeter.
Black Level: Light level of the darker portions of a
video image. A black level control sets the light level of the darkest portion
of the video signal to match that of the display's black level capability. Black
is, of course, the absence of light. Many displays, however, have as much
difficulty shutting off the light in the black portions of an image as they do
creating light in the brighter portions. CRT-based displays usually have better
black levels than DLP, plasma, and LCD, which rank, generally, in that order.
Boost: To increase, make louder or brighter; opposite of
Bridging: Combining two channels of an amplifier to make
one channel that's more powerful. One channel amplifies the positive portion of
an audio signal and the other channel amplifies the negative portion, which are
then combined at the output.
Brightness: For video, the overall light level of the
entire image. A brightness control makes an image brighter; however, when it is
combined with a contrast, or white level control, the brightness control is best
used to define the black level of the image (see Black Level). For audio,
something referred to as bright has too much treble or high-frequency sound.
Cascading Crossovers: Two crossovers used in series on the same signal in
the same frequency range causing greater attenuation of the out-of-band signal.
For example, using the crossover in a receiver's bass management setting and the
one in a subwoofer simultaneously will create an exaggerated loss of signal.
Cathode Ray Tube: (CRT) Analog display device that
generates an image on a layer of phosphors that are driven by an electron gun.
CD: Compact Disc. Ubiquitous digital audio format. Uses
16-bit/44.1-kHz sampling rate PCM digital signal to encode roughly 74 or 80
minutes of two-channel, full-range audio onto a 5-inch disc.
CD-R: Recordable Compact Disc
CD-RW: Rewritable Compact Disc
CEA: Consumer Electronics Association. An association of
manufacturers of consumer electronics products.
Center Channel: The center speaker in a home theater
setup. Ideally placed within one or two feet above or below the horizontal plane
of the left and right speakers and above or below the display device, unless
placed behind a perforated screen. Placement is important, as voices and many
effects in a multichannel mix come from this speaker.
Channel: In components and systems, a channel is a
separate signal path. A four-channel amplifier has at least four separate inputs
and four separate outputs.
Chrominance: (C) The color portion of a video signal.
Coaxial: 1) A speaker typically with one driver in the
middle of, and on the same axis as, another driver. 2) An audio or video cable
with a single center pin that acts as the hot lead and an outer shield that acts
as a ground.
Codec: Mathematical algorithms used to compress large
data signals into small spaces with minimal perceived loss of information.
Coloration: Any change in the character of sound (such as
an overemphasis on certain tones) that reduces naturalness.
Component Video: A signal that's recorded or transmitted
in its separate components. Typically refers to Y/Pb/Pr, which consists of three
75-ohm channels: one for luminance information, and two for color. Compared with
an S-video signal, a Y/Pb/Pr signal carries more color detail. HDTV, DVD, and
DBS are component video sources, though most DBS material is transcoded to
component from composite signals.
Compound Loading: See Isobarik.
Composite Video: A signal that contains both chrominance
and luminance on the same 75-ohm cable. Used in nearly all consumer video
devices. Chrominance is carried in a 3.58-mHz sideband and filtered out by the
TV's notch or comb filter. Poor filtering can result in dot crawl, hanging dots,
or other image artifacts.
Contrast: Relative difference between the brightest and
darkest parts of an image. A contrast control adjusts the peak white level of a
Controller: Generic term that typically refers to a
combination preamp/surround processor or receiver. Can also refer to a handheld
Crossover: A component that divides an audio signal into
two or more ranges by frequency, sending, for example, low frequencies to one
output and high frequencies to another. An active crossover is powered and
divides the line-level audio signal prior to amplification. A passive crossover
uses no external power supply and may be used either at line level or, more
commonly, at speaker level to divide the signal after amplification and send the
low frequencies to the woofer and the high frequencies to the tweeter.
Crossover Frequency: The frequency at which an audio
signal is divided. 80 Hz is a typical subwoofer crossover point and is the
recommended crossover point in theatrical and home THX systems. Frequencies
below 80 Hz are sent to the subwoofer; signals above 80 Hz are sent to the main
Crossover Slope: The rate of attenuation expressed in
decibels of change for every octave away from the crossover frequency.
CRT: See Cathode Ray Tube.
Cut: To reduce, lower; opposite of boost.
Damping: Of or pertaining to the control of vibration by electrical or
Damping Material: Any material that absorbs sound waves
and eliminates acoustic energy by converting it into a different form. Fibrous
material, for example, turns acoustic energy into heat via friction.
D'Appolito: Vertically symmetrical driver array.
Typically consists of a tweeter mounted between two woofers. Creates a
more-vertically directional sound with evenly spaced lobes in the off-axis
response when compared with asymmetrical driver arrays.
DBS: Direct Broadcast Satellite. Term that replaced DSS
to describe small-dish, digital satellite systems such as DirecTV and Dish
Decibel (dB): A logarithmic measurement unit that
describes a sound's relative loudness, though it can also be used to describe
the relative difference between two power levels. A decibel is one tenth of a
Bel. In sound, decibels generally measure a scale from 0 (the threshold of
hearing) to 120-140 dB (the threshold of pain). A 3dB difference equates to a
doubling of power. A 10dB difference is required to double the subjective
volume. A 1dB difference over a broad frequency range is noticeable to most
people, while a 0.2dB difference can affect the subjective impression of a
Delay: The time difference between a sonic event and its
perception at the listening position (sound traveling through space is delayed
according to the distance it travels). People perceive spaciousness by the delay
between the arrival of direct and reflected sound (larger spaces cause longer
Diaphragm: The part of a dynamic loudspeaker attached to
the voice coil that produces sound. It usually has the shape of a cone or dome.
Diffusion: In audio, the scattering of sound waves,
reducing the sense of localization. In video, the scattering of light waves,
reducing hot spotting, as in a diffusion screen.
Diffusor: Acoustical treatment device that preserves
sound energy by reflecting it evenly in multiple directions, as opposed to a
flat surface, which reflects a majority of the sound energy in one direction.
Digital Theater Systems: See DTS.
Digital Audio Server: Essentially a hard drive, a digital
audio server stores compressed audio files (like MP3 or WMA). Most include the
processing to make the files, and all have the ability to play them back.
D-ILA: Direct Drive Image Light Amplifier. This
Hughes/JVC technology uses a reflective LCD to create an image. A light source
is then reflected off the reflective LCD and is directed through a lens to a
Dipole: Speakers with drivers on opposite faces that are
wired electrically out of phase, creating an area of cancellation to the sides.
Recommended by THX for use as surround speakers, with null directed at the
listener to create a more ambient and non-localizable effect.
Direct-Stream Digital: A format for encoding
high-resolution audio signals. It uses a 1-bit encoder with a sampling rate of
2,822,400 samples per second (verses 44,100 for CD). Used to encode six
high-resolution channels on SACD.
Direct-View Television: Display whose image is created on
the surface from which it is viewed.
Dispersion: The spread of sound over a wide area.
Distortion: Any undesired change in an audio signal
between input and the output.
DLP: Digital Light Processing. A Texas Instruments
process of projecting video images using a light source reflecting off of an
array of tens of thousands of microscopic mirrors. Each mirror represents a
pixel and reflects light toward the lens for white and away from it for black,
modulating in between for various shades of gray. Three-chip versions use
separate arrays for the red, green, and blue colors. Single-chip arrays use a
color-filter wheel that alternates each filter color in front of the mirror
array at appropriate intervals.
DMD: Digital Micromirror Device. Texas Instruments engine
that powers DLP projectors. Uses an array with tens of thousands of microscopic
mirrors that reflect a light source toward or away from the lens, creating an
image. Each mirror represents a pixel. See DLP.
DNR: Dynamic Noise Reduction. A signal-processing circuit
that attempts to reduce the level of high-frequency noise. Unlike Dolby NR, DNR
doesn't require preprocessing during recording.
Dolby B: A noise-reduction system that increases the
level of high frequencies during recording and decreases them during playback.
Dolby C: An improvement on Dolby B that provides about
twice as much noise reduction.
Dolby Digital: An encoding system that digitally
compresses up to 5.1 discrete channels of audio (left front, center, right
front, left surround, right surround, and LFE) into a single bitstream, which
can be recorded onto a DVD, HDTV broadcast, or other form of digital media. When
RF-modulated, it was included on some laser discs, which requires an RF-demodulator
before the signal can be decoded. Five channels are full-range; the .1 channel
is a band-limited LFE track. A Dolby Digital processor (found in most new
receivers, preamps, and some DVD players) can decode this signal back into the
5.1 separate channels. Most films since 1992's Batman Returns have been recorded
in a 5.1 digital format, though a number of films before that had 6-channel
analog tracks that have been remastered into 5.1.
Dolby EX: An enhancement to Dolby Digital that adds a
surround back channel to 5.1 soundtracks. The sixth channel is matrixed from the
left and right surround channels. Often referred to as 6.1. Sometimes referred
to as 7.1 if the system uses two surround back speakers, even though both
speakers reproduce the same signal. Software is backwards-compatible with 5.1
systems, but requires an EX or 6.1 processor to obtain additional benefit.
Dolby Pro Logic: An enhancement of the Dolby Surround
decoding process. Pro Logic decoders derive left, center, right, and a mono
surround channel from two-channel Dolby Surround–encoded material via matrix
Dolby Pro Logic II: An enhanced version of Pro Logic.
Adds improved decoding for two-channel, non-encoded soundtracks and music.
Dome: A type of speaker-driver shape; usually used for
tweeters (convex). Concave domes are usually referred to as "inverted domes."
Dope: A tacky substance added to paper cones to damp
spurious vibrations that can cause breakup and rough response. Also, see Editor.
Dot Crawl: An artifact of composite video signals that
appears as a moving, zipper-like, vertical border between colors.
Driver: A speaker without an enclosure; also refers to
the active element of a speaker system that creates compressions and
rarefactions in the air.
DSD: See Direct Stream Digital.
DSP: Digital Signal Processing. Manipulating an audio
signal digitally to create various possible effects at the output. Often refers
to artificially generated surround effects derived from and applied to
DTS: Digital Theater Systems. A digital sound recording
format, originally developed for theatrical film soundtracks, starting with
Jurassic Park. Records 5.1 discrete channels of audio onto a handful of laser
discs, CDs, and DVDs. Requires a player with DTS output connected to a DTS
DTS ES: An enhanced version of the 5.1 DTS system. Like
Dolby's Surround EX, a sixth channel is added. In some cases (DTS ES Discrete),
the sixth channel is discrete. Software is backwards-compatible with 5.1
systems, but requires an ES or 6.1 processor to obtain additional benefit. Neo:6
is a subset of DTS ES that creates 6.1 from material with fewer original
DTV: Digital Television. Umbrella term used for the ATSC
system that will eventually replace our NTSC system in 2006. HDTV is a subset of
the DTV system. While the FCC does not recognize specific scan rates in the
adopted DTV system, typically accepted rates include 480i, 480p, 720p, and
D-VHS: Digital VHS. Digital signals recorded onto
magnetic tape. Greater capacity than typical VHS; can record compressed HDTV
signals. See D-Theater
DVD: Officially known as the Digital Video Disc, though
marketers unofficially refer to it as the Digital Versatile Disc. DVD uses a
5-inch disc with anywhere from 4.5 Gb (single layer, single-sided) to 17 Gb
storage capacity (double-layer, double sided). It uses MPEG2 compression to
encode 720:480p resolution, full-motion video and Dolby Digital to encode 5.1
channels of discrete audio. The disc can also contain PCM, DTS, and MPEG audio
soundtracks and numerous other features. An audio-only version, DVD-A uses MLP
to encode six channels of 24-bit/96-kHz audio.
DVD-A: Digital Versatile Disc-Audio. Enhanced audio
format with up to six channels of high-resolution, 24-bit/96-kHz audio encoded
onto a DVD, usually using MLP lossless encoding. Requires a DVD-A player and a
controller with 6-channel inputs (or a proprietary digital link) for full
DVD-R: A recordable DVD format similar to CD-R in that it
is a write-once medium. Backed by Pioneer, Panasonic, Toshiba, and others.
DVD-RW: A recordable DVD format similar to CD-RW in that
it is re-recordable medium. Backed by Pioneer, Panasonic, Toshiba, and others.
DVD+R: A recordable DVD format similar to CD-R in that it
is a write-once medium. Backed by Sony, Philips, Yamaha, HP, and others.
DVD+RW: A recordable DVD format similar to CD-RW in that
it is re-recordable medium. Backed by Sony, Philips, Yamaha, HP, and others.
DVD-RAM: A recordable DVD format similar to DVD-RW in
that it is a re-writeable format. Unlike DVD-RW it is capable of being written
to and erased over 100,000 times. Backed by Hitachi, Panasonic, Toshiba, and
DVI: Digital Visual Interface. Connection standard
developed by Intel for connecting computers to digital monitors such as flat
panels and DLP projectors. A consumer electronics version, not necessarily
compatible with the PC version, is used as a connection standard for HDTV tuners
and displays. Transmits an uncompressed digital signal to the display. The
latter version uses HDCP copy protection to prevent unauthorized copying. See
Dynamic Range: The difference between the lowest and the
highest levels; in audio, it's often expressed in decibels. In video, it's
listed as the contrast ratio.
EDTV: Extended Definition Television. This CEA-adopted term (though
originally mentioned in an April '99 HT article by Mike Wood and Mike McGann) is
defined as those products that can display DTV images as 480p or higher.
Efficiency Rating: Level of sound output measured at a
prescribed distance with a standard input power. Efficiency rating standard is 1
watt (2.83V at 8 ohms) at 1 meter over a specified frequency range and is
measured in decibels.
Electrostatic: One of the oldest speaker design
principles, electrostatic speakers are generally comprised of two fixed
perforated panels with a constant high-voltage charge applied to them. In
between these two panels is an extremely low-mass diaphragm to which the audio
signal is applied, causing it to move. There are variations on this
construction, but all electrostatic speakers are free from the magnets and voice
coils used in conventional speakers.
Enclosure: The container of air that surrounds the rear
of a speaker driver.
Enhanced for 16:9: See Anamorphic.
Enhanced for Widescreen: See Anamorphic.
EQ: See Equalization or Equalizer.
Equalization: Loosely, any type of relative frequency
adjustment. Specifically, the process of changing the frequency balance of an
electrical signal to alter the acoustical output.
Equalizer: A component designed to alter the frequency
balance of an audio signal. Equalizers may be graphic, parametric, or a
combination of both.
EX: See Dolby EX.
External Crossover: A standalone unit. See crossover.
Feedback: The transmission of current or voltage from the output of a
device back to the input, where it interacts with the input signal to modify
operation of the device. Feedback is positive when it's in phase with the input
and negative when it's out of phase.
Fiber Optic Cable: Glass, plastic, or hybrid fiber cable
that transmits digital signals as light pulses.
FireWire: See IEEE 1394.
FM: Frequency Modulated.
Frequency: The number of cycles (vibrations) per second.
In audio, audible frequencies commonly range from 20 to 20,000 cycles per second
(Hz). In video, frequency is used to define the image resolution. Low-frequency
video images depict large objects or images. Higher frequencies depict smaller
objects (finer details).
Frequency Response: A measure of what frequencies can be
reproduced and how accurately they are reproduced. A measurement of 20 to 20,000
Hz ± 3dB means those frequencies between 20 and 20,000 Hz can be reproduced no
more than 3 dB above or below a reference frequency level.
Full-Range: A speaker designed to reproduce the full
range (20 Hz to 20 kHz) of audio frequencies.
Gain: Increase in level or amplitude.
Graphic Equalizer: A type of equalizer with sliding
controls that create a pattern representing a graph of the frequency-response
changes. Raising sliders boosts the affected frequencies; lowering sliders cuts
(attenuates) the affected frequencies.
Gray Scale: The ability for a video display to reproduce
a neutral image color with a given input at various levels of intensity.
Hanging Dots: An artifact of composite video signals that appears as a
stationary, zipper-like, horizontal border between colors.
HDCP: High-Bandwidth Digital Content Protection. Created
by Intel, HDCP is used with HDTV signals over DVI and HDMI connections and on
D-Theater D-VHS recordings to prevent unauthorized duplication of copyright
HDR: Hard-Drive Recorder. Device that uses a computer
hard drive to store compressed digital audio and video signals.
HDMI: HDTV connection format using a DVI interface that
transfers uncompressed digital video with HDCP copy protection and multichannel
HDTV: High-Definition Television. The high-resolution
subset of our DTV system. The FCC has no official definition for HDTV. The ATSC
defines HDTV as a 16:9 image with twice the horizontal and vertical resolution
of our existing system, accompanied by 5.1 channels of Dolby Digital audio. The
CEA defines HDTV as an image with 720 progressive or 1080 interlaced active (top
to bottom) scan lines. 1280:720p and 1920:1080i are typically accepted as
high-definition scan rates.
Hi-Fi Stereo: Feature found on VCRs that records or plays
back stereo soundtracks with improved fidelity compared to using the linear
High Gain Screen: Material that reflects more light than
a reference material. Increases a projector's light output at the expense of
High Pass: A filter that passes high frequencies, and
attenuates low frequencies. Same as low cut.
Home Theater in a Box: A complete home theater system in
one box (or at least sold together as a package). Consists of five or more
speakers, a subwoofer, and a receiver. May also include a DVD player.
Horn: A type of speaker that looks like a horn. These
speakers have small drivers and very large mouths; the horn shape serves to
transform the small radiating area of the driver into the much larger radiating
area of the mouth of the horn.
Hz: Hertz or cycles per second. Something that repeats a
cycle once each second moves at a rate of 1 Hz.
IEEE 1394: Networking standard for PCs. Combined with 5C copy protection,
is used as a two-way connection to transfer the MPEG-compressed digital
bitstreams between consumer electronics items, including HDTV tuners and
displays, D-VHS recorders, DVD players, and DBS receivers. Also called FireWire,
iLink: See IEEE 1394.
Integrated Amplifier: A combination preamp and amplifier.
Interconnects: Any cable or wire running between two
pieces of A/V equipment. For example, RCA terminated cables connecting pre/pros
Interlace: Process of alternating scan lines to create a
complete image. In CRT displays, every second field/frame is scanned between the
first field/frame. The first field represents the odd lines; the second field
represents the even lines. The fields are aligned and timed so that, with a
still image, the human eye blurs the two fields together and sees them as one.
Interlace scanning allows only half the lines to be transmitted and presented at
any given moment. A 1080i HD signal transmits and displays only 540 lines per
60th of a second. 480i NTSC transmits and displays only 240 lines per 60th of a
second. Motion in the image can make the fields noticeable. Interlaced images
have motion artifacts when two fields don't match to create the complete frame,
often most noticeable in film-based material.
Inverted Dome: A type of speaker-driver shape; usually
used for tweeters (concave).
Imaging: The ability to localize the individual sound
sources in three-dimensional space.
Impedance: A measure of the impediment to the flow of
alternating current, measured in ohms at a given frequency. Larger numbers mean
higher resistance to current flow.
Isobarik: Also known as compound loading. By using two
low frequency drivers (generally mounted face-to-face and wired electrically
out-of-phase or mounted front-to-back in a shallow tube and wired electrically
in phase) you can halve the volume of the cabinet without reducing the low
frequency extension of the subwoofer.
Keystone: A form of video image distortion in which the top of the
picture is wider than the bottom, or the left is taller than the right, or vice
versa. The image is shaped like a trapezoid rather than a rectangle.
kHz: Kilohertz or one thousand Hz.
Laser Disc: Now-defunct 12-inch disc format with excellent analog,
FM-recorded video image, and either analog or CD-quality PCM-encoded audio.
Later discs used one of the analog channels to record an RF-modulated Dolby
Digital/AC3 soundtrack and/or used the PCM tracks to encoded a DTS soundtrack.
LCD: Liquid Crystal Display. A display that consists of
two polarizing transparent panels and a liquid crystal surface sandwiched in
between. Voltage is applied to certain areas, causing the crystal to turn dark.
A light source behind the panel transmits through transparent crystals and is
mostly blocked by dark crystals.
LCOS: Liquid Crystal on Silicon
Letterbox: Format used widely on laser disc and many DVDs
to fit wide-aspect-ratio movies (1.85:1 and 2.35:1, for example) into a smaller
frame, such as the 1.78:1 area of an anamorphic DVD or the 1.33:1 area of a
laser disc or video tape. The image is shrunk to fit the screen, leaving blank
space on the top and bottom. This process sacrifices some vertical detail that
must be used to record the black bars.
LFE: Low Frequency Effects track. The .1 channel of a
Dolby Digital, DTS, or SDDS soundtrack. The LFE is strictly low-frequency
information (20 to 120 Hz, with 115 dB of dynamic range) that's added to the
soundtrack for extra effect. This track does not inherently contain all the bass
of the soundtrack.
Line-Level (Low-Level): A level of electrical signals too
low to make the average speaker move sufficiently. Amplifiers receive line-level
signals and amplify them to speaker level.
LNB: Low-Noise Blocker. The receiving end of a satellite
Low Pass: A filter that lets low frequencies go through
but doesn't let high frequencies go through. Same as high cut.
Luminance: The black and white (Y) portion of a
composite, Y/C, or Y/Pb/Pr video signal. The luminance channel carries the
detail of a video signal. The color channel is laid on top of the luminance
signal when creating a picture. Having a separate luminance channel ensures
compatibility with black-and-white televisions.
Megachanger: CD or DVD player with massive disc storage capacity, holding
50 or more discs.
MHz: Megahertz, or 1 million Hz.
Midbass: The middle of the bass part of the frequency
range, from approximately 50 to 100 Hz (upper bass would be from 100 to 200 Hz).
Also used as a term for loudspeaker drivers designed to reproduce both bass and
Midrange: The middle of the audio frequency range. Also
used as a term for loudspeaker drivers designed to reproduce this range.
MLP: Meridian Lossless Packing. Encoding format that is
able to completely reconstruct the original signal at the receiving end. No
information is lost or discarded, regardless of how trivial it might be. Used to
encode six channels of high-resolution audio on DVD-A.
Mono: Monophonic sound. One channel.
MP3: MPEG-1 Audio Layer-3. Compression scheme used to
transfer audio files via the Internet and store in portable players and digital
Multiple-Rate Encoding: Instead of locking encoding at a
certain constant data rate, it allows the codec to choose whatever rate is best
for that portion of the recording. Usually reduces file size with proportionally
less loss in quality.
Multisource: System with multiple sources. Can also be
used to describe a receiver that can provide multiple different sources into
Multiroom: System that provides audio or video to
multiple areas. Usually with only one source.
Multizone: System that provides different sources into
multiple areas simultaneously.
N-curve: See Academy Curve.
Negative Gain Screen: Material that reflects less light
than a reference material. Often used for DLP and LCD projection systems.
Noise: An unwanted portion of a signal such as hiss, hum,
whine, static, or buzzing.
NTSC: National Television Standards Committee.
Government-directed committee that established the U.S. color TV standard in
1953. Also known, sarcastically, as Never Twice the Same Color or Never The Same
Color due to the inherent difficulty in achieving proper color calibration.
Octave: The difference between two frequencies where one is twice the
other. For example, 200 Hz is an octave higher than 100 Hz. 400 Hz is one octave
higher than 200 hz.
Ohm: A measure of how much something resists (impedes)
the flow of electricity. Larger numbers mean more resistance.
Optical Digital Cable: Fiber optic cable that transfers
digital audio signals as light pulses.
Passive: Not active. A passive crossover uses no external power and
results in insertion loss. A passive speaker is one without internal
Passive Radiator: A radiating surface (usually similar to
a conventional speaker cone) that is not electrically driven but shares the same
air space in a sealed cabinet with an electrically driven loudspeaker. This
arrangement is functionally similar to a loudspeaker with a vented (ported)
cabinet, with the passive radiator serving the duties of the air in the port.
Parametric: Equalizer with adjust-able parameters, such
as center frequency and bandwidth (Q), as well as amplitude.
PCM: See Pulse Code Modulation.
Phase: Time relationship between signals; it's all
Piezo: A type of speaker driver that creates sound when a
quartz crystal receives electrical energy.
Pixel: Contraction of picture element. The smallest
element of data in a video image.
Plasma: Flat-panel display technology that ignites small
pockets of gas to light phosphors.
Port: An aperture in a loudspeaker enclosure that helps
extend the usable low-frequency output. A ported enclosure is also called vented
or bass reflex.
Power Amp: See Amplifier.
Power Output: A measure, usually in watts, of how much
energy is modulated by a component.
Preamplifier: A control and switching component that may
include equalization functions. The preamp comes in the signal chain before the
Pre Outs: Connectors that provide a line-level output of
the internal preamp or surround processor.
Pre Outs/Main Ins: Connectors on a receiver that provide
an interruptible signal loop between the output of the internal preamp or
surround processor portion of the receiver and the input of the amplifier
portion of the receiver.
Pre/Pro: A combination preamp and surround processor.
Processors: Anything that processes an incoming signal in
some way. Surround processors, for example, can decode a Dolby Digital signal to
send to an amp so you can hear it.
Progressive Scanning: Each frame of a video image is
scanned complete, from top to bottom, not interlaced. For example, 480p means
that each image frame is made of 480 horizontal lines drawn vertically. Computer
images are all progressively scanned. Requires more bandwidth (twice as much
vertical information) and a faster horizontal scan frequency than interlaced
images of the same resolution.
Projection System: Display that projects image onto a
Pulse Code Modulation: (PCM) a way to convert sound or
analog information to binary information (0s and 1s) by taking samples of the
sound and record the resulting number as binary information. Used on all CDs,
DVD-Audio, and just about every other digital audio format. It can sometimes be
found on DVD-Video.
PVR: Personal Video Recorder. Marketing term for Video
Q: The magnification or resonance factor of any resonant device or
circuit. Also the width of affected frequencies in an equalizer. Shaped somewhat
like an adjustable width bell curve.
RCA Jacks: Receptacles for coaxial cables carrying line-level audio
signals. Also called phono-type connectors.
Re-EQ: Short for Re-equalization. A feature found on
THX-certified receivers and pre/pros. Movie soundtracks are mixed for theaters
or far-field monitors with an expected high-frequency roll-off otherwise known
as an X-curve. If these soundtracks are not re-mixed for home use, they will
sound too bright when played back through home speakers or near-field monitors.
Re-EQ inserts an X-curve response into the signal to compensate for this, which
takes out some of the soundtrack's excess edginess or brightness.
Rear-Projection Television: Display that projects an
image on the backside of a screen material, usually after having been reflected
off of a mirror.
Receiver: Any component that receives, or tunes,
broadcast signals, be it NTSC, HDTV, DBS, or AM/FM radio. Typically refers to
the single component that includes a preamp, surround processor, multichannel
amplifier, and AM/FM tuner.
Resonant Frequency: The frequency at which any system
vibrates naturally when excited by a stimulus. A tuning fork, for example,
resonates at a specific frequency when struck.
Reverberation: The reflections of sound within a closed
Reverberation Time: The amount of time it takes the
reverberation to decay 60 dB from the level of the original sound.
RF: Radio Frequency. Television signals are modulated
onto RF signals and are then demodulated by your television's tuner. VCRs and
DBS receivers often include channel 3 or 4 modulators, allowing the output
signal to be tuned by the television on those channels. Also, laser discs used
an RF signal for modulating Dolby Digital 5.1 soundtracks on some movies. This
requires an RF demodulator (usually referred to as an AC3-RF demodulator) before
or in the surround processor to decode the signal.
RGB: Red, Green, Blue. Can refer to an unprocessed video
signal or the color points of a display device. Together these three colors make
up every color seen on a display device.
Ribbon Speaker: A loudspeaker that consists of a thin,
corrugated, metallic ribbon suspended in a magnetic field. The ribbon acts
electrically like a low-impedance voice coil and mechanically as a diaphragm.
RMS: Root Mean Square or the square root of the
arithmetic mean (average) of the square's set of values. A reasonably accurate
method of describing an amplifier's power output.
RPTV: Rear-Projection Television
SACD: Super Audio CD. Enhanced audio format with up to six channels of
high-resolution audio encoded using DSD. Requires an SACD player. Multichannel
also requires a controller with six-channel analog or proprietary digital inputs
for full playback.
Sampling Frequency: How often a digital sample is taken
of an analog wave. The more samples taken, the more accurate the recording will
be. You need to sample at a minimum of twice the highest frequency you want to
capture. For example, the 44.1-kilohertz sampling rate of a CD cannot record
sounds higher than 22.05 kilohertz.
Scan Lines: The lines drawn by an electron gun in a CRT
system to make up the picture. Drawn horizontally, from left to right, starting
at the top left and working to the bottom right.
SDTV: Standard Definition Television. Lower resolution
subset of the ATSC's DTV system. 480i is typically accepted as an SD signal.
Digital broadcasters can offer multiple sub-programs at SDTV quality, as opposed
to one or two HD programs. Digital satellite and digital cable often refer to
the majority of their programs as SDTV, somewhat erroneously, as neither system
has anything to do with DTV, though both, technically, consist of a digital 480i
Sealed: See Acoustic Suspension.
Sensitivity: A measurement (in dB) of the sound-pressure
level over a specified frequency range created by a speaker driven by 1 watt
(2.83V at 8 ohms) of power with a microphone placed 1 meter away.
Signal-to-Noise Ratio: A comparison of the signal level
relative to the noise level. Larger numbers are better.
Soft-Dome Tweeter: A tweeter that uses a soft fabric or
plastic dome as the radiating diaphragm.
Soundfield: The total acoustical characteristics of a
space, such as ambience; number, timing, and relative level of reflections;
ratio of direct to reflected sound; RT-60 time; etc.
Soundstage: The area between two speakers that appears to
the listener to be occupied by sonic images. Like a real stage, a soundstage
should have width, depth, and height.
Source: A component from which the system's signals
originate. DVD player, AM/FM tuners, and VCRs are sources.
Speaker: A component that converts electrical energy into
Spider: Part of a loudspeaker driver's suspension that
helps center the diaphragm and returns it to rest after being moved by an
energized voice coil.
SPL: Sound-Pressure Level. Measured in dB.
Subwoofer: A speaker designed to reproduce very low bass
frequencies, usually those below about 80 Hz.
Suspension: The elements that hold a loudspeaker driver's
moving parts together, allows them to move, and helps return them to rest. Most
commonly, these include the flexible surround around the outer rim of the driver
and the spider on the underside of the diaphragm. See Spider.
S-VHS: Super VHS. Enhancement to regular VHS that offers
improved luminance resolution. (400 lines or so.)
S-Video: See Y/C.
Tactile Transducer: A device that turns electrical energy into mechanical
energy, usually used to shake the seating in a theater. Effective in providing
visceral impact without increasing the system's actual SPL level.
THD: Total Harmonic Distortion
3:2 Pulldown Recognition or 3:2 Inverse Telecine: Film is
usually recorded at 24 frames per second. NTSC video (North America) is 30
frames (60 fields) per second. In order to get smooth motion, the film frames
are broken into video fields in a 3-2-3 sequence. 3 fields for the first film
frame, 2 fields for the second film frame, and so on. If a line doubler doesn't
compensate for the extra field during playback on a progressive-scan display,
the image will have noticeable motion artifacts. A line doubler with 3:2
pulldown recognition or 3:2 inverse telecine can see this sequence in the signal
and correct for it by making sure the last field in the first frame isn't mixed
with the first field of the second frame.
THX: Certification program for home theater equipment.
Uses some proprietary features, but mostly assures a base quality level for a
given room size. (See THX Select or Ultra.) Is compatible with any and all
soundtrack formats. Stands for either Tom Holman's eXperiment, after the
engineer who drafted the original standard, or is named after the company's
founder George Lucas' first movie, THX 1138. Nobody agrees on which.
THX Select: Certification program for speakers and
receivers that assures a base level of quality and performance when played in a
room that's between 2,000 and 3,000 cubic feet.
THX Ultra: Certification program for speakers, receivers,
and amplifiers that assures a base level of quality and performance when played
in a room that's greater than 3,000 cubic feet.
THX Ultra 2: The newest certification from THX, THX Ultra
2 requires amplification for seven channels, boundary compensation for
subwoofers, and stricter requirements for amplifiers and speakers than THX
Ultra. Dipole speakers are used for the side surround channels. Monopole
speakers are used for the surround back channel and are placed next to each
other. The Ultra 2 processor accommodates both 5.1 EX/ES soundtracks, as well as
multichannel audio recordings by directing ambient sounds to the dipole speakers
and discrete effects/sounds to the back channels.
Transducer: Any device that converts one form of energy
into another form of energy, specifically when one of the quantities is
electrical. Thus, a loudspeaker converts electrical impulses into sound
(mechanical impulses), a microphone converts sound into electrical impulses, a
solar cell converts light into electricity, etc.
Transmission Line: A (sub)woofer cabinet design where the
driver is mounted at one end of a tube with the same diameter as the radiating
area of the driver and a length of 1/4 wavelength of the 3dB down frequency.
This "tube" may or may not be round and may be folded to decrease the size of
Tuner: See Receiver.
Tweeter: A speaker driver designed to reproduce high
frequencies; usually those over approximately 5,000 to 10,000 Hz.
Uniformity: Even distribution across a given space. In video, uniformity
can refer to the distribution of light (hot spotting) or color.
Unity Gain: Output that equals the input. Unity gain
screen material reflects as much light as the reference material. Has an even
dispersion of light.
Universal Remote: Remote that has the commands of
numerous brands stored into memory and can control several different devices
VAS: The volume of air that offers the same degree of restoring force on
the loudspeaker driver's cone as that of the cone's suspension.
VCR: See Video Cassette Recorder.
VCR Plus: VCR feature that, once programmed, allows the
user to input the TV guide code for a given program into the VCR, which then
automatically sets itself to record that program.
Vented: See Port or Passive Radiator.
VHS: Vertical Helical Scan (or as JCV calls it, "Video
Home System"). Widely used method of recording audio and video electrical
signals onto magnetic tape.
Video Cassette Recorder: Device that records audio and
video electrical signals onto magnetic tape (aka videotape recorder).
Volt: The unit of electrical potential, or difference in
electrical pressure, expressing the difference between two electrical charges.
Watt: A unit of power or energy. One horsepower is equal to 745.7 watts.
Word Length: The sampling rate determines how often an
analog wave is sampled; the word length determines the resolution of the sample.
The larger the word length, the more accurate the sample as a whole. A 16-bit
word length (CD) allows 65,536 different level or volume steps that can be
chosen for each sample.
WMA: Windows Media Audio. An audio compression format
similar to MP3, but with digital rights management (copy protection and usage
restrictions) built-in by Microsoft.
Woofer: A speaker driver designed to reproduce low
Wow-and-Flutter: A measurement of speed instability in
analog equipment usually applied to cassette transports and turntables. Wow is
slow-speed variations, and flutter is fast-speed variations. Lower percentages
X-over: see crossover.
X-curve: An intentional roll-off in a theatrical system's
playback response above ~2kHz at 3dB per octave. A modern convention
(standardized between 1975 and 1984) specified in ISO Bulletin 2969, it is
measured at the rerecording position in a dubbing stage or two-thirds of the way
back in a movie theater. Pink noise should measure flat to 2kHz and then should
roll-off above that. Home THX processors add this roll-off, when engaged, so
that a home video soundtrack will have the same response as it would in a
Y/C: Abbreviation for luminance/ chrominance, aka S-video signal. Color
and detail signals are kept separate, thus preventing composite video artifacts.
Cable uses four-pin connector. Used with S-VHS VCRs, DVD players, Hi-8, and DBS
Y/Pb/Pr: See component video.
Zone: One or more rooms powered by one or more amplifiers, which are all
fed by one source. A home can be divided into multiple zones, which can play
multiple sources, even though several rooms (say, the kitchen, dining room, and
living room) all play the same source.