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NOAA/NWS Computer and Communications
Terms and Acronyms

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NWS Unique Terms and Acronyms

Nota Bene: If there are terms and acronyms that you use routinely that are missing from this list, please tell us about them so that we may add them to the list.

Communications Terms and Acronyms Starting with the Letter A

ACD ... automated call distribution

ACN ... AWIPS Communication Network [AWIPS]

ACU ... Acquisition Control Unit

ADCCP     Advanced Data Communications Control Procedures: the American
          National Standards Institute (ANSI) version of a HDLC protocol that is
          used for synchronous transmission of data.  

ADAS ... AWOS Data Acquisition System (FAA)

ADDL ... Advanced Development and Demonstration Laboratory

ADP ... automated data processing

AFOS ... Automation of Field Operations and Services

AFPS ... AWIPS Forecast Preparation System

AI ... artificial intelligence

Amplifier: A device used to increase the strength of an analog signal.

AMSU ... advanced microwave sounding unit

Analog     A signal, such as voice, that varies in a continuous manner. 
Signal      (Contrast with Digital signal)

ANSI ... American National Standards Institute [AWIPS]

AO ... automated observation

AOMC ... ASOS Operations and Monitoring Center

API ... Application Programmer Interface [AWIPS]

APPN ... Advanced Peer-to-Peer Networking

ARC ... automatic remote collector

ARP ... address resolution protocol

ARP     Address Resolution Protocol: The TCP/IP  network-layer protocol that
          translates an (32 bit) IP address into a (48 bit) physical layer address.

ART      The Automatic Radiotheodolite, ART, is a ground-based radio
         direction finder that automatically tracks a ballon-borne radiosonde.

ART Description ART Pictures ASOS Automated Surface Observing System: NWS system of weather sensor equipment.

ASOS Description ASOS Pictures

AS1 ... Application Server 1 [AWIPS]

ASOS     Automated Surface Observing System: NWS system of
         weather sensor equipment.

ASOS Description ASOS Pictures ASOS Comms Diagram

ATM ... asynchronous transfer mode

ATM ... automated teller machine

AUI ... Application User Interface [AWIPS]

AVHRR ... Adveanced Very High Resolution Radiometer

AWIPS   Advanced Weather Interactive Processing System: NWS Computer system for
        ingesting and displaying weather data for NWS Forecast Offices and River
        Forecast Centers. 

AWIPS Summary Description

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Terms Starting with the Letter B

Bandwidth - The frequency range between the lowest and highest frequencies
            that are passed through a component, circuit, or system with
            acceptable attenuation.

Baseband - The frequency band occupied by a single signal in it's original or unmodulated

Baseband  -  A method of signaling in which only one signal occurs on the tranmission
signaling     media at any given point in time.

Baud     A unit of signaling speed equal to the number of signal events per second.
          Not necessarily the same as bits per second (bps).
bis     Meaning second in Latin, this term is used as a suffix to denote a secondary
          version of a ITU modem standard.

Bit rate - The speed at which bits are transmitted, usually expressed in 
            bits-per-second. Not neccessarily the same as baud rate.

BMP ... bitmap (type of electronic image)

bootp - Network protocol which allows systems to get configuration/boot information
         from some other more authoritative or more intelligent system typically residing 
         on the local LAN.

bps      (bits per second) A measure of the information transfer rate of a channel.

BPI ... bits per inch

BPS ... bits per second

Bridge    A device that expands a local area network by forwarding packets based
          on the (48 bit) physical address. In OSI terminology, a bridge operates at
          the Data Link Layer (layer 2). 

Broadband - A method of signaling in which multiple signals share the bandwidth of the transmission by the subdivision of the bandwidth into channels based on frequency.

Browser - A program that is used as a GUI (Graphical User Interface) for retrieving and viewing html documents (Web Pages) from the World-Wide-Web (Internet). Documents are transferred using the http protocol.

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Terms Starting with the Letter C

CAD ... computer-aided design

CADD ... computer-aided design and drafting

CAI ... computer-aided instruction

carrier - A signal suitable for modulation by another signal containing information
          to be transmitted. The carrier is usually a sine wave for analog systems.

CCITT - Consultative Committee for International Telephone and Telegraph

CD ... compact disk

CD-ROM ... compact disk, read-only memory

cell     A 53-byte-long transmission unit used by ATM. Each cell has a 5-byte header 
         and 48-byte payload.

channel, voice grade - A channel, generally with a frequency range of about 300 to
                       400 Hz, suitable for transmission of speech or data in
                       analog form. Data transmission rates of 9600 Bps can be
                       achived by modulation techniques that produce a baud rate
                       of 2400.

CIR ... committesysinformation rate

client - A workstation/program which requests a network service from another system.

Comms    A device that connects many terminals to a LAN through one 
Server    network connection.  The terminal may be remoted through a modem.
          This is also sometimes called a terminal server.

Pictures of Terminal/Comm Server

committesysinformation rate - The minimum operating rate supported by a frame-relay service.

connection-oriented - A type of communication in which a connection must be established
                      between the sender and receiver before transmission occurs.

contention - The facility provided by dial networks or a port selector that allows
              multiple terminals to compete on a first-come-first-served basis for
              a smaller number of computer ports

COTS ... Commercial Off-the-Shelf (software and hardware) [AWIPS]

View info on AWIPS CP

CRON      - A UNIX utility that can automatically start jobs/programs at 
            specified times, dates, day-of-week, etc...

CPU ... central processing unit

CRS       = Console Replacement System for NOAA Weather Radio. 
CRS Description
CRS Pictures

CRT ... cathode ray tube

CSMA/CD   Carrier Sense Multiple Access with Collision Detect: a local area network
          access technique in which multiple stations connected to the same
          channel are able to sense transmission activity on the channel and to
          defer the initiation of transmission while the channel is active. In addition
          the stations are able to detect the interference caused by simultaneous
          transmissions by 2 or more stations (collisions) and to retransmit colliding
          messages in an orderly manner.

 CSU      Channel Service Unit terminates the high-speed circuit, performs signal
          regeneration, monitors for bipolar violations, and performs remote
          loopback testing.  A CSU can be used on either a T1 or a fractional T1.

View NEXRAD CSU Info. View DSU/CSU pic.

CW ... continuous wave

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Terms Starting with the Letter D

daemon   A UNIX program that runs as a background process (similiar to a DOS TSR)

DAT ... digital audio tape

DATACOL ... software system supporting RFC gateway functions

db ... decibel

DBMS ... Data Base Management System

DC ... direct current

DCE      Data Communications Equipment: The equipment that provides the
          functions required to establish, maintain and terminate a
          connection, and that provides the signal conversion required
          for communication between data terminal equipment and telephone
          line or data circuit.

DSX-1     Actual data rate achieved on a DS-1 (T1) minus the 8k of framing bits/sec
          that is equal to 1.536Mbps. Term is used in 88D 520 manual.

DCP ... data collection platform (satellite)

DCP ... data collection package (ASOS)

DDT ... design, development and test

DFD ... Data Flow Diagram [AWIPS]

demodulation - The process of recovering data from a modulated carrier wave.
                The reverse of modulation.

DIFAX ... digital facsimile

  DNS     Domain Name System: The distributed name and address mechanism
          used in the Internet.

DOS ... disk operating system

DSU       Digital Service Unit converts incoming digital data into the bipolar format
          for transmission over a T1 or fractional T1. Fractional T1 can operate at
          speeds up to 56Kbps or 64kbps clear channel.

View DSU/CSU pic.

DSU/CSU   With divestment of the Bell system the DSU and CSU functions may be
          combined in one unit.

 DS-1     Digital signaling rate of 1.544Mbps used on T1 

DTE      Data Terminal Equipment. A computer that provides data in the form of
          digital signals as it's output.

DS1 ... Data Server 1 [AWIPS]

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Terms Starting with the Letter E

Eb/No ... Energy per Bit over Noise density associated with the SBN operation [AWIPS]

Ethernet  A 10Mbps bus standard for LANs using the IEEE 802.3 frame and
          CSMA/CD but address and control slightly differ from 802.3.  Ethernet and
          802.3 require different software drivers (See OSI model).

Download ETHERNET cbi course

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Terms Starting with the Letter F

FDDI      Fiber Distribution Data Interface: a high-speed (100Mbps) LAN standard.
          The underlying medium is fiber optics, and the typical topology consists of 
          dual-attached, counter-rotating rings. IEEE 802.8 is the standard for

FDDI pictures Download FDDI cbi course FDM Frequency Division Multiplexer: A device that divides the available transmission frequency range into narrower bands, each of which is used for a separate channel.

FEP ... front-end processor

FIPS ... Federal Information Processing Standard

Firewall - Equipment and/or software configured to provide enhanced security between networks.

Flow-control: The orderly regulation of the flow of data by the use of special characters (inband signaling) or control signals at the RS232 interface (outband signaling)

FM ... frequency modulation

FORTRAN ... Formula Translation Language (programming language) [AWIPS]

Frame-relay : A packet switched service that does not provide for error detection
              and correction, resulting in minimal routing delays.

Frame_relay Circuit components diagram FTP File Transfer Protocol: A TCP/IP protocol that lets a user on one computer access and transfer files to and from another computer over a network.

FTS ... Federal Telephone System

Full Duplex - Refers to a communications system or equipment capable of
              simultaneous two-way communication.

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Terms Starting with the Letter G

Gateway   In the TCP/IP world a router is referred to as a gateway because it is the
          gateway to wide area networking. For everybody else a gateway is the
          device that allows a network to access the facilities of another network.

gated     A UNIX routing program that supports multiple routing protocols

GIF ... graphics interface format (type of electronic image)

GMT ... Greenwich mean time

GOES ... Geostationary Operational Environmental Satellite

GOES-NEXT ... Next Generation Geostationary Operational Environmental Satellite

GOSIP ... Government Open Systems Interconnection Profile

GTA ... ground to air

GTE ... General Telephone Spacenet [AWIPS]

GTS ... Global Telecommunication System

GUI ... Graphical User Interface [AWIPS]

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Terms Starting with the Letter H

Half-duplex - Refers to a communications system or equipment capable of communication
              in both directions, but in only one direction at a time.

Handshaking - Exchange of predetermined codes and signals between two data terminals
              to establish a connection.

HCI (HI) ... Human Computer Interface [AWIPS]

HCL ... Hydrologic Command Language [AWIPS]

HDLC  High-level Data Link Control. ITU standard for bit-oriented, data-link
     control protocol, with error correction that is used for synchronous data

HF ... high frequency

HIPS ... High Resolution Picture Transmission (HRPT) Image Processing System

HIRS ... high-resolution infrared sounder

HIRS-2 ... high-resolution infrared sounder, version 2

HIRS-3 ... high-resolution infrared sounder, version 3

HMI ... Human/Machine Interface [AWIPS]

Host     Term used to refer to a TCP/IP workstation.

HP-UX A version of the UNIX operating system that is used on Hewlett Packard systems.

HRDI ... high-resolution Doppler imager

HRIR ... high-resolution infrared radiometer

HRPT ... high-resolution picture transmission

HSP ... hard-wired signal processor

HTTP    Hyper-Text Transfer Protocol - a protocol used to transfer html documents over
         the Internet/Intranet. The protocol is invoked through the use of a client
         program called a browser.

HTML    Hyper-text Markup Language a computer coding language used to create text/graphics 
        documents suitable for viewing via a browser(see HTTP).

hub	A piece of equipment used in Ethernet/10BaseT LANs to connect multiple
        workstations or devices together logically and physically to a single 
        location. The hub has multiple RJ-45 connectors. Internally it has a
        single bus.

Pocket-Hub Pictures

Hz ... hert

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Terms Starting with the Letter I

IEEE - Institute of Electrical and Electronic Engineers (U.S.)
SUMMARY CHART of IEEE 802 Standards

IEEE 802.2     A data link layer control (LLC) standard used with 802.3, 802.4, 802.5 and

IEEE 802.3     A physical layer standard specifying a linear (bus) LAN using CSMA/CD
               access method. Ethernet is a similar standard but not an IEEE
               encapsulation. Usually 10Mbps.

IEEE 802.4 A physical layer standard specifying a linear (bus) LAN using token- passing access method. Usually 10Mbps. IEEE 802.5 A physical layer standard specifying a ring topology LAN using token- passing access method. IBM's token ring follows this standard. May operate at 4Mbps or 16Mbps.

IEEE 802.8 A specification for a (FDDI) Fiber Distributed Data Interface LAN to connect to a fiber optic transmission system using the token-passing access method.

IFPS - Interactive Forecast Preparation System (used in AWIPS). Forecasters use IFPS to create a digital database of predicted weather elements from which a suite of text, tabular, and image forecast products are automatically created and formatted. View IFPS Training
Informix - Commercial (Relational) Database Management System (RDBMS) used in AWIPS. Download Introductory NWSTC Informix O.V. materials View online NWSTC DB/Informix concepts overview doc. Informix Web-Site Interface - A shared boundary defined by common physical interconnection characteristics, signal characteristics, and meanings of interchanged signals. Internet - A network term for that is most commonly used to describe a collection of networks interconnected with routers. Intranet - An Internal WAN not directly connected to the Internet. IP - Internet Protocol is the network layer protocol for a connectionless, best- effort packet delivery service. Is used to route packets through a switched network. CLICK HERE for more information on IP addressing CLICK HERE for online instruction on IP addressing IPX/SPX - a protocol stack used in Novell LANs

IR ... Infrared

IS ... Information systems

ISDN      Integrated Services Digital Network: A communication offering designed to
          provide a universal digital network that will enable the integration of
          voice and data on a common telephone facility.

ISO       International Standard organization. Volunteer organization involved
          with developing standards for computers and networks.

IT ... Information technology

ITU     An International standards committee.  Formally known as CCITT.

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Terms Starting with the Letter J

JCL ... job control language

jet-direct - a NIC(network interface card) licensed to Hewlett Packard specifically
             designed for connecting peripherals such as printers/plotters directly
             to a LAN.

jitter - a tendency toward lack of synchronization caused by mechanical or electrical changes.

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Terms Starting with the Letter K

kb ... kilobit

kbps ... kilo bits per second [AWIPS]

kB ... kilobyte

kernel   A term used in operating systems to mean the core O/S. The kernel is responsible
         for the low-level functions such as hardware management.

kHz ... kilohertz

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Terms Starting with the Letter L

LAN: (see Local Area Network)

LAPM Link Access Protocol for Modems. A ITU link layer (HDLC ) protocol built-in
     to modems for V.42 error correction.

LAPB     Link Access Protocol Balanced. A HDLC protocol part of the X.25
         standard for access to a packet switching network.
View info. on LAPB use in NEXRAD

LAPD     Link Access Protocol for D-channel. Originally developed as an HDLC
         protocol for ISDN and is also used in frame relay networks.

LAPS ... Local Analysis and Prediction System

LARC ... limited automated remote collector (replaced DARDC)

LBC ... laser beam ceilometer

LDAD : Local Data Acquisition and Dissemination (external interface to AWIPS)
View info on AWIPS LDAD
View LDAD diagrams/add'l info.

LDS ... Lightning Detection System

LED ... light-emitting diode

LEDWI ... light-emitting diode weather indicator [ASOS]

Linux - a derivative of the UNIX operating system which runs on Intel and other PC platforms.

Local Area Network : A communications network that is restricted to a small geographic
                     area, usually within a building or on a campus, and that has
                     cabling normally installed or controlled by the organization that
                     operates the network.

View more detailed LAN definition/info. Local loop : The pair of wires between a phone customer terminal and the central office. Loopback test : A test of a communications link performed by connecting the equipment output of one unit to the equipment input of the other unit and testing the quality of the received signal.

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Terms Starting with the Letter M

mbps ... mega bits per second

MHz ... megahertz

MIME ... multipurpose Internet mail extension

MIS ... Management Information System

MNP     An acronym for the Microcom Inc. protocols called Micro Networking
        Protocol. MNP is divided into 10 classes. Two MNP modems negotiate to
        the highest mutually supported class. MNP classes 2-4 error correction
        and MNP 5 data compression has been licensed to many modem

Modem - MOdulator/DEModulator: A type of DCE that at the transmitting end converts
        digital data to an analog signal for transmission on telephone circuits.
        A modem at the receiving end converts the analog signal to digital form.

View Modem Circuit diagrams Download MODEMS cbi course modulation - The process of varying some characteristics of the carrier wave in accordance with the instantaneous value or samples of the intelligence to be transmitted. Amplitude, frequency, and phase are the characteristics commonly varied.

MPEG ... Movie Picture Expert Group

Multiplex - To interleave or simultaneously transmit two or more messages on a single

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Terms Starting with the Letter N

NCF       Network Control Facility: NWS & PRC managed help desk facility for AWIPS.
          NCF tel# = 301-713-1284

NCF Web-Site

NESDIS : National Environmental Satellite Data and Information Service

NetBeui  - a protocol stack used in native MicroSoft LANs     

NetCDF :  NETwork Common Data Form : data storage and retrieval software
          interface and file structure used in AWIPS. NetCDF provides
          portable, self-describing data files particularly suitable to
          uniform multi-dimensional data sets.

Network Interface Card - a computer board/card that is used to connect the computer
                         to the local network.  

View card and connector pics ansysinfo NEXRAD: NEXt generation RADar: The NEXRAD system is an interconnected system of Doppler meteorological radars (WSR-88Ds) destined for approximately 175 sites throughout the continental United States, in portions of Alaska, Hawaii and Puerto Rico, and at selected overseas military bases.

NEXRAD Description NEXRAD Pictures NFS Network File System: is software that lets a client program running on one computer use a networked server computer's disk drive as if it were a local disk. It is a Sun Microsystems distribution that has been licensed to hundreds of products. NIC Network Interface Card (see Network Interface Card) NIS Network Information Service: Formally called "yellow pages" this software allows configuration files such as passwd, hosts, etc... to be managed in a single location and sharable across the LAN. node = a piece of equipment (computer/Host, device ...) at a location on a network. Noise - Random electrical signals, introduced by circuit components or natural disturbances, that tend to generate errors in transmission. Novell Netware Family of networking operating systems based on the SPX/IPX protocols for the transport-layer. Null Modem View null modem cable/pin config. NWSTG : National Weather Service Telecommunications Gateway

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Terms Starting with the Letter O

ORDA ... open radar data acquisition

ORPG ... open radar product generator

OS ... Operating system

OSI       OPEN SYSTEMS INTERCONNECTION. A 7-layer network protocol model designed 
          by the ISO committees intended to be the international standard computer
          network architecture.

View more detailesysinformation on the OSI model OSPF Open Shortest Path First: A gateway protocol that utilizies actual time vectors to determine the best routing for messages (as opposed to RIP which uses hops).

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Terms Starting with the Letter P

PBX       Private Branch eXchange: Telephone switching equipment dedicated to one
          customer and connected to the public switched network.

PPP Point-to-Point Protocol: The standard serial protocol for communication to the Internet. PPP has an HDLC error correction that SLIP was lacking. PPP can be used for both synchronous and asynchronous data. Polling The individual selection of multiple terminals by a controller to allow transmission of traffic to and from all terminals on a multidrop line in an orderly manner. Port A logical pointer to an TCP/IP application such Telnet, FTP etc.

POSIX ... Portable Operating System Interface [AWIPS]

PPP ... point-to-point protocol

Print Server - A computer or device which serves as the interface and control
               mechanism to a network accessible printer.

Protocol  A formal description of message formats and rules that equipment must
          follow to exchange those messages. A group of protocols interfacing
          together, such as in a LAN, are referred to as a stack.
          (See OSI layered architecture)

Protocal Analyzer - A device that decodes a bit stream being monitored into
                    characters that represent the format ansysinformation content 
                    of a transmitted protocol

PTM ... point to multipoint

PTP ... point to point

PVC       Permanent Virtual Circuit: A logical connection between endpoints in a
          network that remains in place until the network administrator tears it

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Terms Starting with the Letter Q

No terms defined.

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Terms Starting with the Letter R

RADID ... radar information display

RAM ... random access memory

RARP  Reverse Address Resolution Protocol. The Internet protocol that finds the
      IP address to match a known physical address. It is primarily used by
      diskless workstations.

Repeater  In 802 Ethernet a repeater is used to extend the segment by simply
          regenerating the electrical signal. The electrical signal is considered the
          physical or OSI layer 1.

RCM ... radar coded message

RDA ... radar data acquisition [WSR-88D]

RDBMS ... Relational database management system [AWIPS]

RF ... radio frequency

RFI ... radio frequency interference

RJE ... remote job entry

RIP     Routing Information Protocol: An Interior routing protocol supplied with
        UNIX and most routers. RIP is used to update routing tables in a network
        that uses routers. (OSPF is a newer protocol being widely used in routers).

ROSA ... Remote Observation System Automation

Router     A device that forwards traffic based on network-layer or the IP address in
           TCP/IP.  These are usually smart devices that can provide alternate
           routes if one is down.
Router pictures

CLICK HERE for online instruction on routing & gateways/routers

Routing   A network-layer function whereby a network device determines where to
          send packets across the network based on the network-layer address.

RPG ... remote product generator

RPG ... radar product generator [WSR-88D]

RPGOP ... radar product generator operational position [WSR-88D]

RPM ... revolutions per minute

RS-232    An interface standard between the Data Terminal Equipment (Com port)
          and the Data Communications Equipment (modem).

RS-422A   Standard for data signaling, using 2-wire balanced transmission.

RS-449 An interface standard between DTE and DCE using balanced transmission of data. Uses a DB-37 connector and may have a DB-9 connector for secondary channel.

RS-530 An interface standard that uses balanced data transmission and DB25 connector.

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Terms Starting with the Letter S

SBN ... Satellite Broadcast Network

SCSI ... Small Computer Systems Interface

Serial transmission - A method of information transfer in which the bits that
                      compose a character are sent in sequence one at a time.

SLIP Serial Link Interface Protocol: A non-standard network layer protocol that allows for point-to-point communications via TCP/IP across a serial line. Lacks the error correction capabilities of PPP but is satisfactory for direct computer-to-computer links. SMTP Simple Mail Transfer Protocol: An applications layer protocol used for sending and receiving mail. It also provides specifications for functional third party E-mail system (CC-MAIL) interaction and control.

SNMP ... Simple Network Management Protocol

SNMP   Simple Network Management Protocol: A protocol used by network
       components, such as bridges, routers, and other intelligent network
       management devices, to exchange network-management information.

SPX/IPX   SPX is the transport layer protocol developed by Novell. SPX is not used
          much even by Novell. The IPX protocol has proven to be fast and
          efficient, particularly with the relatively small data packets---in the 512 byte
          range--- usually requested by DOS and Windows applications. IPX is
          bundled in most network operating systems including Windows, Windows NT,
          LANtastic, and Power Lan. However IPX's small packets aren't
          desirable on wide area networks, where TCP/IP is preferred, but IPX
          packets are more effective on a Local Area Network.

SQL ... structured query language

Socket    A port number combined with IP address that identifies a particular
          Address logical connection in use by an application system.

subnet    A portion of a network that shares a network address with other subnets but is
          distinguised by a unique subnet number. A subnet is to a network as a network is
          to an internet. 

Subnet address / number - a part of the IP address which designates the locally administered subnet subnet mask - a number which is used in a network (i.e. Internet) used to interpret which IP address bits are used for network, subnetwork (see subnet above), and host identification. CLICK HERE for online instruction on subnetting swap - information normally utilized in computer memory that has been written to temporary disk space because of limited memory. Switch Switching Hub: a multiport Ethernet device designed to increase network performance by allowing only essential traffic on the attached individual Ethernet segments. Packets are filtered or forwarded based upon their source and destination physical addresses. The distinction between bridges and switches has become blurred. Switch is now used to refer to a multiport device that operates at Ethernet wirespeed.

Switch pictures Synchronous transmission - Transmission in which the sending and receiving instruments are operating continuously at substantially the same frequency and in which the desired phase relationship can be maintained by means of correction.

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Terms Starting with the Letter T

T1     Term for digital carrier used to transmit DS-1 (1.544Mbps) formatted data.
       Term often used for DS-1 signaling speed.

TCP     An Internet transport protocol to provide reliable, connection-oriented, full-
        duplex bit streams.

TCP/IP    Transmission Control Protocol/ Internet Protocol: an internet transport
          protocol providing reliable, connection-oriented, full-duplex bit streams
          with IP's ability to route packets through a WAN.

CLICK HERE for online instruction on TCP/IP

TCP/IP    Or TCP/IP stack (See OSI layers): A group of protocols developed for internetworking
Suite     systems with differing computing platforms ( i.e. IBMs with DECs with PCs 
          with Unix etcetera ) over a LAN or a WAN. Also used on the Internet.            
          Includes IP, ICMP, TCP, UDP, FTP, Telnet, SMTP, SNMP, TFTP

TDM       Time Division Multiplexer: A device that allows the transmission of
          two or more independent data channels on a single high-speed circuit
          by interleaving the data from each channel on the circuit by time.

Telnet The virtual terminal protocol that lets users on one host access another host and work as terminal users of the remote host. Terminal - A device that connects many terminals to a LAN through one network Server connection. The terminal may be remoted through a modem. Pictures of Terminal/Comm Server TFTP Trivial File Transfer Protocol: A TCP/IP protocol that lets a user on one computer access and transfer files to and from another computer over a network. For TFTP as opposed to FTP this is usually done with much less user intervention/overhead and can be done automatically without user/password access.

TIFF ... taged image file format

Topology - The 'shape' a network takes, such as a star (with a centralized hub) or 
           a bus (equipment strung on one open-ended cable serially from end to end), 
           a ring (circular closed-ended cable(s), etcetera...


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Terms Starting with the Letter U

UART      Universal Asynchronous Receiver/Transmitter: A device that performs
          asynchronous communication functions by converting parallel digital
          output from a DTE into serial bit transmission and vice versa.

UDP User Datagram Protocol: an Internet transport protocol that exchanges datagrams without acknowledgments or guaranteed delivery.

UDP ... User Datagram Protocol [AWIPS]

UHF ... ultra high frequency

UNIX	A powerful networkable multi-user operating system. In the NWS UNIX is used in
        AWIPS, and CRS. Currently there is no single UNIX standard but rather several 
        variants including AIX, HP-UX, Linux, Solaris, SCO, UNIXWare, etcetera...

UNIX reference pages
NWSTC UNIX courses (Intro, SA, SysSpt, NetSec, INFORMIX)

UNIXWare - a verion of UNIX formally distributed by Novell but now owned by SCO. UNIXware is 
           used in CRS

UPS ... uninterruptible power supply

URL ... uniform resource locator (Internet address)

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Terms Starting with the Letter V

V.22bis   ITU standard for 2400 bps, full duplex, transmission over a switched
          telephone network.

V.24     ITU standard for DTE to DCE interface. Nearly equivalent to RS-232.

V.25     ITU standard for an automatic call unit, often internal to the modem, for
         dialing from an asynchronous DTE port only.

V.25bis   ITU standard for an automatic call unit, often internal to the modem, for
          dialing from an asynchronous or synchronous DTE port.

V.32     ITU standard for 9.6 Kbps, full duplex, transmission over a switched
         telephone network.

V.32bis   ITU standard for 14.4 Kbps, full duplex, transmission over a switched
          telephone network.

V.34     ITU standard for 28.8 Kbps, full duplex, transmission over a switched
         telephone network.

V.35     ITU DTE-DCE interface standard that is no longer published but still
         widely used. The term has come to refer to a high speed,low capacitance,
         shielded interface with a  34-pin winchester connector. V.35 interface is
         common on bridges, routers and DSU/CSUs.

V.42     ITU standard for error correction at the modem for asynchronous data
         only. Also the mechanism for negotiating: (1) LAPM (HDLC) or (2) MNP 2-
         4 error correction.

V.42bis   ITU standard for data compression at the modem for asynchronous data
          only. V.42 error correction must be established first and then V.42bis will
          negotiate for V.42bis (Lempel-Ziv) or MNP 5 data compression.

Voice     Has been established with a bandwidth of 0 hz to 4000 hz, however the
channel   effective bandwidth is  300 hz to 3000 hz  at -3dB points after phone
          company filtering and the electrical characteristics of the local loop.

VHF ... very high frequency

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Terms Starting with the Letter W

WAN      Wide Area Network: A network that covers a wide geographic area. 

WSR ... weather surveillance radar

WSR-57 ... weather surveillance radar - 1957

WSR-74C ... weather surveillance radar - 1974

WSR-88D ... Doppler weather surveillance radar


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Terms Starting with the Letter X

X-Terminal - a graphical (X-Windows) display which must get it's configuration 
             information from another device.

XMODEM - A half-duplex file transfer protocol limited to transmitting one file at
         a time.

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Terms Starting with the Letter Y

YMODEM - A half-duplex file transfer protocol that supports the transfer
         of multiple files.

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Terms Starting with the Letter Z

ZMODEM - A full-duplex file transfer protocol that supports the transfer of multiple
         files and enables a previously interrupted transmission to be resumed at the
         point of interruption.

Zyplex   Comms/terminal Server used in AWIPS.

Zyplex pictures

Terms Starting with a number

10Base2 : An IEEE standard for thin coax (ThinNet) Ethernet network.
          (10mps - Baseband transmission - 200 meters)

10BaseT : An IEEE 802.3 standard for unsheilded Twisted-pair Ethernet network. (10mps - Baseband transmission)

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NWSTC - Updated 02-08-05

Webmaster : David S. Rowell