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Glossary of Industrial Networking Terms

10BASE2 - IEEE802.3 (or Ethernet) implementation on thin coaxial cable (RG58/AU).
10BASE5 - IEEE802.3 (or Ethernet) implementation on thick coaxial cable.
10BASET - IEEE802.3 (or Ethernet) implementation on unshielded 22 AWG twisted pair cable.
A/D Conversion Time - This is the length of time a board requires to convert an analog signal into a digital value. The theoretical maximum speed (conversions/second) is the inverse of this value. See Speed/Typical Throughput.
A/D - Analog to Digital conversion.
ACK -  Acknowledge (ASCII - control F).
AFC -  Automatic Frequency Control. The circuit in a radio receiver that automatically keeps the carrier frequency centred in the passband of the filters and demodulators.
AGC -  Automatic Gain Control. The circuit in a radio that automatically keeps the carrier gain at the proper level. Algorithm Can be used as a basis for writing a computer program. This is a set of rules with a finite number of steps for solving a problem.
ALU -  see Arithmetic Logic Unit.
ANSI - American National Standards Institute. The principle standards development body in the USA.
Appletalk - A proprietary computer networking standard initiated by Apple Computer for use in connecting the Macintosh range of computers and peripherals (including Laser Writer printers).
This standard operates at 230 kilobits/second.
ARP - Address Resolution Protocol. A Transmission Control Protocol/Internet Protocol (TCP/IP) process that maps an IP address to Ethernet address, required by TCP/IP for use with Ethernet.
ARQ - Automatic Request for Transmission. A request by the receiver for the transmitter to retransmit a block or a frame because of errors detected in the originally received message.
AS - Australian Standard.
ASCII - American Standard Code for Information Interchange. A universal standard for encoding alphanumeric characters into 7 or 8 binary bits. Drawn up by ANSI to ensure compatibility between different computer systems.
ASIC - Application Specific Integrated Circuit.
ASK - Amplitude Shift Keying. See Amplitude Modulation.
ASN.1 - Abstract Syntax Notation One. An abstract syntax used to define the structure of the protocol data units associated with a particular protocol entity.
AUI CABLE - Attachment Unit Interface Cable. Sometimes called the drop cable to attach terminals to the transceiver unit.
Auto Tracking Antenna - A receiving antenna that moves in synchronism with the transmitting device which is moving (such as a vehicle being telemetered).
AWG - American Wire Gauge.

Balanced Circuit - A circuit so arranged that the impressed voltages on each conductor of the pair are equal in magnitude but opposite in polarity with respect to a defined reference.
BCC - Block Check Character. Error checking scheme with one check character; a good example being Block Sum Check.
BCD - Binary Coded Decimal. A code used for representing decimal digits in a binary code.
BERT/BLERT - Bit Error Rate/Block Error Rate Testing. An error checking technique that compares a received data pattern with a known transmitted data pattern to determine transmission line quality.
Binary Coded Decimal (BCD) - A code used for representing decimal digits in a binary code.
Bipolar Range / Inputs - A signal range that includes both positive and negative values. Bipolar inputs are designed to accept both positive and negative voltages. (Example: ±5 V).
BNC - Bayonet type coaxial cable connector. bps Bits per second. Unit of data transmission rate.
Bridge - A device to connect similar sub-networks without its own network address. Used mostly to reduce the network load.
Broad Band - A communications channel that has greater bandwidth than a voice grade line and is potentially capable of greater transmission rates.
Broadcast - A message on a bus intended for all devices which requires no reply.
BS - Backspace (ASCII Control-H).
BS - British Standard.
BSC - Bisynchronous Transmission. A byte or character oriented communication protocol that has become the industry standard (created by IBM). It uses a defined set of control characters for synchronised transmission of binary coded data between stations in a data communications system.

Cache Memory - A fast buffer memory that fits between the CPU and the slower main memory to speed up CPU requests for data.
CCD - Charge-Coupled Device (camera).
CCIR - Comite Consultatif Internationale des Radiocommunications.
CCITT - Consultative Committee International Telegraph and Telephone. An international association that sets worldwide standards (e.g. V.21, V.22, V.22bis).
CGA - Color Graphics Adapter. A computer standard utilising digital signals offering a resolution of 320 by 200 pixels and a palette of 16 colors.
CMRR - Common Mode Rejection Ratio - A data acquisition’s board's ability to measure only the voltage difference between the leads of a transducer, rejectingwhat the leads have in common. The higher the CMRR, the better the accuracy.
CMV - Common Mode Voltage.
CNR - Carrier to Noise Ratio. An indication of the quality of the modulated signal.
CPU - Central Processing Unit.
CR - Carriage Return (ASCII control-M).
CRC - Cyclic Redundancy Check. An error-checking mechanism using a polynomial algorithm based on the content of a message frame at the transmitter and included in a field appended to the frame. At the receiver, it is then compared with the result of the calculation that is performed by the receiver. Also referred to as CRC-16.
CSMA/CD - Carrier Sense Multiple Access/Collision Detection.

D/A - Digital to Analog.
DAS - Data Acquisition System.
dBi - A unit that is used to represent the gain of an antenna compared to the gain of an isotropic radiator.
dBm - A signal level that is compared to a 1-mW reference.
dBmV - A signal amplitude that is compared to a 1-mV reference.
dBW - A signal amplitude that is compared to a 1-Watt reference.
DCE - Data Communications Equipment. Devices that provide the functions required to establish, maintain and terminate a data transmission connection. Normally it refers to a modem.
DES - Data Encryption Standard.
DFB - Display Frame Buffer.
DIN - Deutsches Institut Fur Normierung.
DIP - Acronym for dual in line package referring to integrated circuits and switches.
DLE - Data Link Escape (ASCII character).
DMA - Direct Memory Access.
DNA - Distributed Network Architecture.
DPLL - Digital Phase Locked Loop.
DR - Dynamic Range. The ratio of the full scale range (FSR) of a data converter to the smallest difference it can resolve. DR = 2n where n is the resolution in bits.
DSP - Digital Signal Processing.
DSR - Data Set Ready. An RS-232 modem interface control signal which indicates that the terminal is ready for transmission.
DTE - Data Terminal Equipment. Devices acting as data source, data sink, or both.

EBCDIC - Extended Binary Coded Decimal Interchange Code. An 8-bit character code used primarily in IBM equipment. The code allows for 256 different bit patterns.
EEPROM - Electrically Erasable Programmable Read Only Memory. This memory unit can be erased by applying an electrical signal to the EEPROM and then reprogrammed.
EIA - Electronic Industries Association. An organisation in the USA specialising in the electrical and functional characteristics of interface equipment.
EIA-232-C - Interface between DTE and DCE, employing serial binary data exchange. Typical maximum specifications are 15m at 19200 Baud.
EIA-423 - Interface between DTE and DCE, employing the electrical characteristics of unbalanced voltage digital interface circuits.
EIA-449 - General purpose 37 pin and 9 pin interface for DCE and DTE employing serial binary interchange.
EIA-485 - The recommended standard of the EIA that specifies the electrical characteristics of drivers and receivers for use in balanced digital multipoint systems.
EIRP - Effective Isotropic Radiated Power. The effective power radiated from a transmitting antenna when an isotropic radiator is used to determine the gain of the antenna.
EISA - Enhanced Industry Standard Architecture.
EMI/RFI - Electro-Magnetic Interference or Radio Frequency Interference. Background 'noise' capable of modifying or destroying data transmission.
ENQ - Enquiry (ASCII Control-E).
EOT - End of Transmission (ASCII Control-D).
ESD - Electrostatic Discharge.

FDM - Frequency Division Multiplexer. A device that divides the available transmission frequency range in narrower bands, each of which is used for a separate channel.
FIFO - First in, First Out.
FIP - Factory Instrumentation Protocol.

GPIB - General Purpose Interface Bus. An interface standard used for parallel data communication, usually used for controlling electronic instruments from a computer. Also designated IEEE-488 standard.

HDLC - High Level Data Link Control. The international standard communication protocol defined by ISO to control the exchange of data across either a point-to-point data link or a multidrop data link.
HF - High Frequency.
HPF - High-Pass Filter. A filter processing one transmission band that extends from a cutoff frequency (other than zero) to infinity.
HPIB - Hewlett-Packard Interface Bus; trade name used by Hewlett-Packard for its implementation of the IEEE-488 standard.

IEC - International Electrotechnical Commission.
IEE - Institution of Electrical Engineers.
IEEE - Institute of Electrical and Electronic Engineers. A US-based international professional society that issues its own standards and, which is a member of ANSI and ISO.
ISB - Intrinsically Safe Barrier.
ISDN - Integrated Services Digital Network. Afairly recent generation of worldwide telecommunications networks that utilize digital techniques for both transmission and switching.
ISR - Interrupt Service Routine. See Interrupt Handler.
ITU - International Telecommunications Union.

LDM - Limited Distance Modem. A signal converter which conditions and boosts a digital signal so that it may be transmitted further than a standard EIA-232 signal.
LED - Light Emitting Diode. A semi-conductor light source that emits visible light or infra red radiation.
LF - Line Feed (ASCII Control-J).
LPF - Low-Pass Filter. A filter processing one transmission band, extending from zero to a specific cutoff frequency.

MOS - Metal Oxide Semiconductor.
MOV - Metal Oxide Varistor.
MSB - Most Significant Byte or Most Significant Bit.
MTBF - Mean Time Between Failures.
MTTR - Mean Time To Repair.

NMRR - Normal Mode Rejection Ratio - The ability of a board to filter out noise from external sources, such as AC power lines. NMRR filtering compensates for transient changes in the incoming signal to provide greater accuracy. The higher the NMRR, the better the filtering of incoming data will be.
NRZ - Non Return to Zero. Pulses in alternating directions for successive 1 bits but no change from existing signal voltage for 0 bits.
NRZI - Non Return to Zero Inverted.

OCR - Optical Character Recognition, optical character reader.
OSI - Open Systems Interconnection. A set of defined protocol layers with a standardized interface which allows equipment from different manufacturers to be connected.

PAD - Packet Access Device. An interface between a terminal or computer and a packet switching network.
PAL - Phase Alternating Lines. This is the television standard used in Europe and Australia. The PAL standard is 25 frames per second with 625 lines.
PCM - Pulse Code Modulation. The sampling of a signal and encoding the amplitude of each sample into a series of uniform pulses.
PDU - Protocol Data Unit.
PEP - Peak Envelope Power. Maximum amplitude that can be achieved with any combination of signals.
PIA - Peripheral Interface Adapter. Also referred to as PPI (Programmable Peripheral Interface).
PLC - Programmable Logic Controller.
PLL - Phase Locked Loop
PSDN -  Public Switched Data Network. Any switching data communications system, such as Telex and public telephone networks, which provides circuit switching to many customers.
PSTN - Public Switched Telephone Network. This is the term used to describe the (analog) public telephone network.

QAM - Quadrature Amplitude Modulation.
QPSK - Quadrature Phase Shift Keying.

RAMDAC - Random Access Memory Digital-to-Analog Converter.
RFI - Radio Frequency Interference.
RLE -  Run Length Encoder. A digital image method whereby the first grey level of each sequential point-by-point sample and its position in the succession of grey levels is encoded. It is used where there is a tendency for long runs of repeated digitized grey levels to occur.
RS - Recommended Standard, for example, RS-232C. More recent designations use EIA, for example, EIA-232C.
RS-232C - Interface between DTE and DCE, employing serial binary data exchange. Typical maximum specifications are 50 feet (15m) at 19200 baud.
RS-422 - Interface between DTE and DCE, employing the electrical characteristics of balanced voltage interface circuits.
RS-423 - Interface between DTE and DCE, employing the electrical characteristics of unbalanced voltage digital interface circuits.
RS-449 - General purpose 37-pin and 9-pin interface for DCE and DTE employing serial binary interchange.
RS-485 - The recommended standard of the EIA that specifies the electrical characteristics of drivers and receives for use in balanced digital multipoint systems.
RTU -  Remote Terminal Unit. Terminal Unit situated remotely from the main control system.

SDLC - Synchronous Data Link Control. IBM standard protocol superseding the bisynchronous standard.
SNA - Systems Network Architecture.
SNR - Signal to Noise Ratio.
STP - Shielded Twisted Pair.

TCP/IP - Transmission Control Protocol/Internet Protocol. The collective term for the suite of layered protocols that ensures reliable data transmission in an internet (a network of packet switching networks functioning as a single large network).
TDM -  Time Division Multiplexer. A device that accepts multiple channels on a single transmission line by connecting terminals, one at a time, at regular intervals, interleaving bits (bit TDM) or characters (Character TDM) from each terminal.

UART -  Universal Asynchronous Receiver/Transmitter. An electronic circuit that translates the data format between a parallel representation, within a computer, and the serial method of transmitting data over a communications line.
USRT - Universal Synchronous Receiver/Transmitter.
UTP - Unshielded Twisted Pair.

VCO -  Voltage controlled oscillator. Uses variable DC applied to tuning diodes to change their junction capacitances. This results in the output frequency being dependent on the input voltage.

WAN - Wide Area Network.