Communications Systems Glossary

ADSL (Asymmetric digital subscriber line).  ADSL (Asymmetric digital subscriber line) allows broadband data services to be carried on conventional copper pair telephone cables.

Aerial.  An aerial (or antenna) is a device for radiating and receiving electromagnetic waves in the radio frequency (RF) range.

Aloha.  Aloha is a multiple-access technique by which a number of terminals can access a shared transmission media.

American Standard Code for Information Interchange.  See ASCII.

Antenna.  An antenna (or aerial) is a device for radiating and receiving electromagnetic waves in the radio frequency (RF) range.

ASCII (American Standard Code for Information Interchange).  ASCII (American Standard Code for Information Interchange) is a code that uses seven bits to represent standard text characters as well as a number of terminal control characters.

Asymmetric digital subscriber line.  See ADSL.

Bandwidth (BW).  The bandwidth is the difference between the minimum and the maximum frequencies that can be passed by a communications system.

Binary.  Binary describes a system having two states that are interpreted as a logical 1 or 0, or "on" or "off".

Bridge.  A bridge is a data-link layer (Layer 2) device that interconnects two local area networks (LANs).

Broadband.  The term broadband is used to describe a broad range of frequencies. In communications systems, broadband can also be used to describe a high-capacity communications system.

Broadcast.  To broadcast is to send the same message to a number (normally all) of the network terminals simultaneously.

BW.  See Bandwidth.

Cable.  A cable is one or more electrical conductors in an insulating sheath.

Cable modem.  A cable modem is a high-speed modem that transmits and receives data over coaxial cables for TV distribution.

Cell.  In personal communications systems (cellular mobile phone systems) a cell is the geographic area served by a single base station. Cells are arranged so that base-station frequencies can be reused between cells. In asychronous transfer mode (ATM) networks, a cell is a packet of data.

Channel.  Strictly, a channel is a single direction path (or simplex path) along which a signal can be sent. However, in common usage the term is synonymous with circuit.

Circuit.  A circuit is the medium connecting two communicating devices, or a path between a transmitting and receiving device (there may be one or more intermediary nodes).

coax.  See Coaxial cable.

Coaxial cable (coax).  A coaxial cable is a transmission medium normally consisting of one central conductor enclosed within a conductive sheath, separated by a dielectric.

Compression.  Compression is the process by which redundancy is removed from data before transmission or storage.

Encryption.  Encryption is a process in which transmitted data (plain text) is scrambled (encrypted) into cipher text at the transmitter and reconstructed into readable data (plain text) at the receiver.

Ethernet.  Ethernet is a local area network (LAN) implementation using the carrier-sense multiple access (CSMA/CD) protocol on a bus topology.

Gateway.  A gateway is an application layer (Layer 7) device that interconnects two local area networks (LANs).

Internet protocol.  See IP.

IP (Internet protocol).  The Internet Protocol (IP) is an internetworking protocol that provides connectionless service across multiple packet-switching networks.

Microwave.  The term "microwave" refers to electromagnetic waves in the frequency range of about 2-40 GHz.

Modem.  Modem is a contraction of modulator/demodulator, which transforms a digital bit stream into an analogue signal (in the modulator), and vice versa (in the demodulator) so that the digital signal can be passed over an analogue channel.

Network.  A network is the interconnection of two or more computers by a communications medium (line, coaxial cable, fibre, IR or RF), together with appropriate hardware and software.

Network manager.  A network manager is an individual responsible for administering, configuring, planning, monitoring, and establishing standards and procedures for a network.

PBX (Private branch exchange).  A PBX (Private branch exchange) is an organisation’s internal telephone exchange.

Private branch exchange.  See PBX.

Protocol.  A protocol is a set of rules or conventions that govern one or more of the many aspects of communication.

Router.  A router is a network layer (Layer 3) device that interconnects two local area networks (LANs).

Server.  A network server, (more traditionally called a file server), is normally a fast processor with large storage and memory capacity, which manages the network and the network file system and provides a number of functions such as: access to printers, disk space, application programs, back-up tape drives, as well as running the network operating system (NOS).

Simple network management protocol.  See SNMP.

SNMP (Simple network management protocol).  The SNMP (simple network management protocol) is used to pass network-management information in TCP/IP networks.

Telephony.  Literally, telephony means "speaking at a distance".

Transceiver.  Transceiver is a contraction of transmitter/receiver-a device that is able to act as both a transmitter and a receiver.

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