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

Amplitude The maximum variation from the zero position of any alternating current; the size or magnitude of an alternating wave form. It is sometimes described as volume, intensity, or loudness.

Amplitude Modulation A form of modulation in which the amplitude of a carrier wave is varied in accordance with some characteristic of the modulating signal.

Analog Signal A continuous signal that varies in voltage to reflect variations in some quantity, such as loudness of the human voice.

Asynchronous Transmission Communications that is not related to a specific timing of the transmission facility. Transmission is characterized by individual characters, or bytes, encapsulated with start and stop bits, from which a receiver derives timing for sampling bits. Sometimes termed start-stop transmission.

Automated Meter Reading (AMR) The technology of automatically reading water and energy meters and transmitting the information to a central data base for billing and statistical analysis purposes.

Automated Metering Infrastructure (AMI) Referring to a family of technologies providing two-way data communications with electric and gas meters. AMI includes automated meter reading but has the ability to do much more, including detection of outages, turning services on and off and providing energy information to the customer.

Bandwidth The range between the lowest and the highest frequencies of a channel. The greater the bandwidth, the more information per unit of time can be transmitted.

Baseband The frequency band occupied by a single or composite signal in its original or un-modulated form before being transmitted.

Baud A unit of signaling speed derived from the reciprocal time of the shortest pulse width in the bit stream.

Bit A contraction that comes from the words binary digit. This is the smallest unit of information in a code using the binary system.

Bit Error Rate (BER) The ratio of bits transmitted in error to the total bits transmitted. A measure of performance and circuit quality in digital transmission systems.

Broadband A synonym for wideband. A communications channel having a bandwidth much broader than that of a voice-grade channel, thereby providing high-speed data transmission capability. Not a specific data rate, but usually rates over 256 kb are considered broad band..

Byte Generally an 8 bit quantity of information, used mainly in referring to data storage and transmission.

Cell A subdivision of a mobile telephone or wireless service area; it contains a low powered radio communicating system connected to the local telephone network.

Cellular radio Technology employing low power radio transmission as an alternative to local wired telephone service; users may be stationary or mobile - in the latter case, they are passed, under the control of a central site, from one cell’s transmitter to an adjoining one.

Channel A communications path for the electrical transmission of information (as voice, data, etc.).

Circuit The complete path between two end-terminals over which one-way or two-way communication can be provided. A circuit may consist of one or more channels connected together to provide the end to end communications.

Code Any system of communication in which arbitrary groups of symbols represent units of plain text or information to be transmitted.

Common carrier An organization in the business of providing communications services to the general public, and which is subject to regulation by the appropriate state and federal agencies.

C-4 Conditioned line A private line telephone circuit that has special electronic equipment added to reduce distortion and improve transmission quality. C-4 is a measure of the level of applied conditioning.

DS-0 (Digital Signal Level 0) A digital signal transmitting 64,000 bits of information per second. In North America, the DS-0 is the basic building block data rate of digital communication systems. All higher data rate systems are normally some multiple of DS-0 channels.

DS-1 (Digital Signal Level 1) A digital signal transmitting 1.544 million bits of information per second. When transported over a telephone circuit it is commonly referred to as a T-1. A DS-1 is composed of 24 DS-0 signals and can transport 24 voice channel equivalent circuits. Note: The DS-1, DS-2, DS-3, etc. are not exact mathematical multiples of the basic DS-0 data rate because of added signaling and control bits.

DS-2 (Digital Signal Level 2) A digital signal transmitting four DS-1 signals or 96 voice channel equivalents.

DS-3 (Digital Signal Level 3) A digital signal transmitting 28 DS-1 signals or 7 DS-2 signals. A DS-3 rate channel operates at approximately 45 million bits per second and has the capacity to transport 672 voice channel equivalent circuits.

Data Digitally represented information, which includes voice, text, facsimile, and video.

Data communications The movement of coded information by means of electronic transmission systems.

Digital signal A nominally discontinuous electrical signal that changes from one state to another in discrete steps. Typically, information is represented by “0’s and 1’s”.

Distributed processing The processing of data at remotely located sites using communication links to interconnect the remotely located micro-computers or intelligent terminals with each other.

Downlink The rebroadcast of a microwave radio signal from a satellite back to earth.

Duplex See full-duplex.

Earth station In satellite communications, a terrestrial communications center that maintains direct links with a satellite.

Facsimile (FAX) The process of transmitting text, pictures, diagrams, etc. via a telecommunication system to a remote location where a printed copy of the transmitted material is reproduced.

Federal Communications Commission (FCC) A board of commissioners appointed by the president of the United States under the authority of the Communication Act of 1934, having the power to regulate all non-governmental radio, microwave and interstate electrical communication systems in the US.

Fiber optics Hair thin filaments of transparent glass or plastic that use pulses of light instead of electricity to transmit voice, video, or data signals.

Frequency The number of cycles or events per unit of time. When the unit of time is one second, the measurement unit is the hertz (Hz).

Frequency modulation (FM) A process in which the intelligence of a signal is represented by variations in the frequency of the oscillation of the signal.

Full-duplex A type of operation in which simultaneous two-way conversations, messages, or information may be passed between any two given points.

Geosynchronous orbit The orbit position where communication satellites will rotate at the same speed as the surface of the earth, remaining stationary over the same earth location (about 23,300 miles above the earth’s equator).

Global Positioning Service (GPS) A satellite system providing terrestrial positioning services anywhere on earth. Low cost receiving equipment decodes the signals received from multiple satellites to provide a relatively accurate fix of the receiver’s location.

Group In analog transmission systems - twelve voice frequency channels multiplexed together into a composite signal. These composite signals may be further combined (see Supergroup) or used directly to modulate (and de-modulate) an analog carrier system.

Hertz (Hz) A unit of measurement representing one cycle-per-second.

Information Processed data (as opposed to raw data).

Interconnect equipment The equipment at each end of a communication channel; also called terminal equipment and customer-premises equipment.

Inter-exchange carrier (IXC) A carrier engaged in transporting voice and data circuits across local access and transport area boundaries. Also referred to as a long distance carrier or long distance company.

Internet A network of computer networks which originally began as a research network linking educational and government research facilities. Now a public access network which includes all types of commercial, educational, personal, government and entertainment information and is growing at an unprecedented rate.

Internet Protocol (IP) A protocol for transmitting digital bits of information over the Internet. IP was originally formulated as a standardized way to control the transmission of digital information, in the form of data, over the Internet. It has grown in popularity and is now the predominant protocol for transmitting information (voice, data and video) over all types of public and private digital networks.

Intranet A network internal to a company allowing employees to access company information using software tools that are similar to those used in the public Internet.

Isochronous In communication systems, meaning two-way communication without delay. Delay is created by some systems that store, queue or buffer the information (voice, data or video) before transmitting, thus adding delay.

Kbps A thousand (kilo) bits per second.

Local Access and Transport Area Any one of 161 geographic areas served by a local exchange telephone company. These areas were defined in the divestiture of the local Bell telephone companies from AT&T in 1984.

Local Area Network (LAN) A configuration of telecommunications facilities designed to provide internal data communications within a limited area (as in a building).

Low Earth Orbit (LEO) satellites Proposed satellite systems consisting of numerous satellites deployed in close proximity to the earth’s surface, often between 400 and 1000 miles in altitude. These will typically operate at mobile radio frequencies and with their limited bandwidth will be suitable for low speed data communications using packet technology.

Mbps A million (mega) bits per second.

Microwave radio Line-of-sight radio transmission using very short wavelengths, corresponding to frequencies above 1,000 megahertz.

Modulation The process, or the result of the process, of varying certain characteristics of a signal in accordance with a message signal to be transmitted (e.g., varying the amplitude, frequency, or phase). Matching the information signal to the communications channel.

Multiple Address Radio System (MAS) Refers to a variety of data telemetry radio systems operating in the UHF spectrum. These systems are characterized by a master station that polls associated remote stations, transferring data and exchanging control signals between remote locations and a centralized control system.

Multi Protocol Label Switching A method of prioritizing data packets in an Internet Protocol based transmission system.

Multiplexer A device that combines a number of low-speed channels into one higher speed channel at one end of a transmission system and divides it back into low-speed channels at the other end.

Network A series of points, nodes or stations connected together by communication channels.

Node In a network, a terminal of any branch of a network or a terminal common to two or more branches of a network.

OC-1 Optical Carrier Level -1. The primary optical carrier data level used in a Sonet system. This is equivalent to an STS-1 signal that has been converted from an electrical to an optical signal. An OC-1 can carry one DS-3 along with other overhead and synchronizing information. The line rate is 51.84 Million bits per second. (See STS-1)

OC-3 Optical Carrier Level -3. An optical carrier data level used in Sonet that has multiplexed (combined) three (3) OC-1’s (see above). This is the second level of multiplexing usually used in a Sonet system. This is equivalent to an STS-3 electrical signal converted to an optical signal. The line rate is 155.52 Million bits per second. (Also see STS-3)

Open wire pairs A communication transmission facility comprised of pairs of bare wire conductors supported on insulators, which are mounted on poles to form an aerial pole line. (Still used today in some rural areas for telephone service.)

Optical fiber See fiber optics

Packet A group of data bits and associated control information that is switched and transmitted as a whole. The data bits can represent voice, video or numerical data information.

PBX Private branch exchange. A private telephone exchange located on the user’s premises and connected to the public telephone network.

Personal Communication Service (PCS) A form of cellular communications using frequencies in the microwave spectrum. These systems provide voice and data communications to hand-held telephone and computing devices to be sold to the general public.

POP Point of Presence. Telephone terminology describing the location of a switch and inter-connection equipment operated by an inter-exchange carrier at which the inter-exchange carrier relays voice calls and data to or from the local exchange carrier’s network.

Private network A configuration of private radio, microwave, fiber or other electronic media interconnected together for the exclusive use of one customer.

Protocol The rules a communication transmission system must follow in order for intelligible communication to take place.

Repeater A device that amplifies an input signal or, in the case of a digital system, amplifies, re-times and reshapes the electronic pulses preparing the signal for re-transmission.

Response time In a data system, the elapsed time between the end of transmission of an inquiry message and the beginning of the receipt of the response message, measured at the inquiry originating station.

Router In a data network, a system interface device that connects two networks together, functioning to intercept the data packets, read the address of the packet and route it to the next router or destination device in the network.

Satellite communications The use of orbiting satellites to relay transmissions from one earth station to one or more other earth stations.

Simplex A circuit affording communications in either direction, but in only one direction at a time. An example would be the use of a two-way radio unit in a truck.

SONET (Synchronous Optical Network) A form of synchronous transmission of information originally designed for fiber optic systems and now available in newer microwave radio equipment. Sonet allows for the transmission of a wide range of data speeds with a minimum of interface equipment.

STS-1 Synchronous Transport Signal Level -1. The primary electrical signal rate used for transporting information in a Sonet system. The line rate is 51.84 million bits per second. This signal forms the base rate for synchronous transport and is multiplexed (combined) to form all the higher data rates employed. (Also see OC-1)

STS-3 Synchronous Transport Signal Level -3. This line rate of 155.2 million bits per second is the next rate up in a Sonet system (See STS-1 above). This is equivalent to three (3) multiplexed (combined) STS-1 signals. (Also see OC-3)

Supergroup Five groups multiplexed together forming one composite signal containing 60 voice frequency channels. See Group.

Synchronization The process of determining and maintaining the correct electronic timing for transmitting and receiving information.

Synchronous transmission Data communications in which characters or bits are sent at a fixed rate; the rate is maintained by electronic clocking devices at both the transmitting and receiving ends of the circuit.

T-1 Carrier (see also DS-1) A multiplexed digital transmission system that provides 24 voice grade channels on one pair of copper wires.

T-1 Data Rate Referring to the transmission of data at the digital signal level one rate(DS-1) rate. The T-1 (DS-1) data rate is 1.544 megabits per second.

Telco A generic abbreviation for telephone company.

Telecom A generic abbreviation for telecommunications.

Telecommunication Any transmission, emission, or reception of information of any kind (sound, voice, images, or data) over a distance by electrical or electromagnetic methods.

Telecommunications Act of 1996 A significant amendment to the Communications Act of 1934 which eliminates barriers to market entry for all types of telecommunications service providers. Full implementation of this act will deregulate all types of telecommunications services.

Terminal equipment Communications equipment at each end of a circuit to permit the stations involved to accomplish the mission for which the circuit was established.

Trunk A single transmission channel between two points, both of which are either switching centers or nodes, or both. Commonly used to describe channels between PBXs or PBXs and the telephone company end offices (telephone trunks).

Ultra High Frequency (UHF) Terminology referring to the band of frequencies in the electromagnetic spectrum ranging from 300 MHz to 3000 MHz.

Very High Frequency (VHF) Terminology referring to the band of frequencies in the electromagnetic spectrum ranging from 30 MHz to 300 MHz.

VSAT Very Small Aperture Satellite Terminal. A small satellite station capable of transmitting and receiving data communications via a satellite based communication system.

Voiceband The range of frequencies used by telephone companies and private telecommunication systems to transmit the human voice, typically from about 300 Hz to 3000 Hz.

Voice channel A channel on an electronic communication system capable of transmitting voice band frequencies.

Voice over IP (VoIP) The process of converting voice conversations to a digital format and then routing them over the Internet or any Internet Protocol based system.

Wide Area Network A configuration of telecommunication facilities providing electronic communications between locations geographically widely separated (as city wide, state wide, inter-state, etc.)

Wideband A communications channel offering a transmission bandwidth much greater than a voice-grade channel. There is no specific definition of wideband in terms of data rates but typically speeds in excess of 256 thousand bits/s are considered “wideband” data rates.