GLOSSARY of SELECTED TELECOMMUNICATIONS TERMS ACCESS: In telephony, a point of entry into a circuit or a network. In computing, the manner in which files or data are referred to by a computer. ANALOG: A process which models information in the form of a continuously varying parameter i.e. current or voltage. BAND: A unit of signalling speed which describes the number of signal changes in one second. Not interchangeable with bits-per-second(bps) because more than one bit may be transmitted in one change in signal state. BANDWIDTH: The range of frequencies available for signalling i.e. the difference between the high and low frequencies of a transmission band normally expressed in cycles per second (hertz). BROADBAND: Also known as wideband, this term refers to a communication channel having a bandwidth greater than a voice-grade channel. BYPASS: The action of hooking up to a long distance or local network without using local telephone company facilities. Bypass technologies include cellular radio, two-way cable television, short haul microwave and direct satellite to rooftop antennas. CARRIER: A high frequency radio signal which is modulated to carry information long distances through space or via cable. CENTREX: A PBX type of service where incoming calls may be dialled direct to extensions without operator assistance. Outgoing and intercom calls may be dialled by extension users. Currently, this service is usually provided by the local telephone company through the local central office. CIRCUIT: A physical transmission path between two or more points. CIRCUIT SWITCHING: A method of communications where an electrical connection between calling and called stations is established on demand for exclusive use of the circuit until the connection is released. COMMON CHANNEL SIGNALLING: A technique in which signalling information relating to a number of circuits, and other information such as that used for Network Management, is conveyed by addressed messages over a single channel dedicated to signalling. DIGITAL: Characteristic of a discontinuous electrical signal which carries information by means of discrete changes in its duration or amplitude. Digital communications has come into wide use as a system for transmitting voice or data information due to its economy and accuracy. ELECTRONIC MAIL: Electronic transmission of a written message to one or more destinations delivered via voice, text, or video form. FACSIMILE: A system for the transmission of images (pictures, maps, diagrams, correspondence etc). The image is scanned at the transmitter, reconstructed at the receiving station, and duplicated on coated paper or film. FIBRE OPTICS: This modern transmission form uses laser technology to produce a beam of light which can be modulated to carry large amounts of information through fine glass fibres. These modulated signals are detected by light-sensitive semi-conductor devices. LOCAL AREA NETWORK (LAN): A term applied to a communications system which allows a number of different kinds of electronic products, including computers, terminals, facsimile devices and printers, to communicate. Such systems usually employ coaxial cable, fibre optics, or traditional twisted pair cable, and extend for at most a few kilometres. NETWORK: A system designed to connect devices for the purpose of transmitting information. Networks are either common to all users or privately leased by customers for their own use. PBX (PRIVATE BRANCH EXCHANGE): A computer which coordinates voice and often, data traffic, and takes the form of either a small switching system installed on a business subscriber's premises or can be as large as Northern Telecom's DMD-250 used in the telephone company's central office. PBXs are also referred to as PABXs (private automatic branch exchanges) or EPABXs (electronic private branch exchanges). PUBLIC SWITCHED NETWORK: The network of more than 3500 Canadian switching centres which are available for public use. SATELLITE (COMMUNICATIONS): An object or vehicle orbiting, or intended to orbit, the earth, moon, or other celestial body. TERMINAL: Any device capable of sending and/or receiving information over a communications channel and also a point at which information can enter or leave a communication network. VERY SMALL APERTURE TERMINAL SERVICE (VSAT): A satellite-based service providing full duplex digital data transmission between satellite earth stations and broadcast video transmission. Used by businesses requiring low cost high performance branch office to headquarters broadcast video and data transmission. WIDE AREA TELEPHONE SERVICE (WATS): A service enabling a customer to direct dial long distance calls to subscribed zones on a measured bulk rate, rather than for each individual call.