Telecom Dictionary - Definitions of terms
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
T
T - Abbreviation for tera (1012). See International System of Units.
T-1 - - A leased line connection that can carry 1,544,000 bits per second. The T-1 carrier is the most commonly used digital transmission service in the United States, Canada, and Japan. It consists of 24 separate channels using pulse code modulation (PCM) signals with time-division multiplexing (TDM). T-1 lines were originally designed to transmit digitized voice signals. Current applications also include digital data transmission. T1 lines originally used copper wire but now also include optical and wireless media. A T-1 Outstate System has been developed for longer distances between cities.
Internet access providers are commonly connected to the Internet as a point-of-presence (POP) on a T1 line owned by a major telephone network. Many businesses also use T1 lines to connect to an Internet access provider.
See T-carrier.
T-3 - A leased line connection that can carry 44,736,000 bits per second. The T-3 carrier is a digital transmission that consists of 672 individual channels, each of which supports 64 Kbps using pulse code modulation (PCM) signals with time-division multiplexing (TDM). T-3 lines were originally designed to transmit digitized voice signals. Current applications also include digital data transmission. T3 lines originally used copper wire but now also include optical and wireless media. A T-3 Outstate System has been developed for longer distances between cities.Internet access providers are sometimes connected to the Internet as a point-of-presence (POP) on a T3 line owned by a major telephone network. Some businesses also use T3 lines to connect to an Internet access provider.
T1 (carrier) - The generic designator for any of several digitally multiplexed telecommunications carrier systems. Note 1: The designators for T-carrier in the North American digital hierarchy correspond to the designators for the digital signal (DS) level hierarchy. See the associated table below. Note 2: T-carrier systems were originally designed to transmit digitized voice signals. Current applications also include digital data transmission. Note 3: If an "F" precedes the "T", a fiber optic cable system is indicated at the same rates. Note 4: The table below lists the designators and rates for current T-Carrier systems. Note 5: The North American and Japanese hierarchies are based on multiplexing 24 voice-frequency channels and multiples thereof, whereas the European hierarchy is based on multiplexing 30 voice-frequency channels and multiples thereof. - See T-carrier.
T1 Line - A full-duplex digital transmission facility that is composed of transmission media (optical or metallic) and regenerators that carry one DS1 signal.
T3 (carrier) - A dedicated leased phone line connection supporting data rates of 44,736,000 bits per second. A T-3 line actually consists of 672 individual channels, each of which supports 64 Kbps.
T-3 lines are used mainly by Internet Service Providers (ISPs) connecting to the Internet backbone and for the backbone itself.
T-3 lines are sometimes referred to as DS3 lines. - See T-carrier.
T3 Line - A full-duplex digital transmission facility that is composed of transmission media (optical or metallic) and regenerators that carry one DS3 signal.
Tactical Automatic Digital Switching System (TADSS) - A transportable store-and-forward message-switching system used for rapid deployment in support of tactical forces.
Tactical Command and Control (C2) Systems - The equipment, communications, procedures, and personnel essential to a commander for planning, directing, coordinating, and controlling tactical operations of assigned forces pursuant to assigned missions.
Tactical Communications - Communications in which information of any kind, especially orders and decisions, are conveyed from one command, person, or place to another within the tactical forces, usually by means of electronic equipment, including communications security equipment, organic to the tactical forces. Note: Tactical communications do not include communications provided to tactical forces by the Defense Communications System (DCS), to nontactical military commands, and to tactical forces by civil organizations.
Tactical Communications System - A communications system that (a) is used within, or in direct support of, tactical forces, (b) is designed to meet the requirements of changing tactical situations and varying environmental conditions, (c) provides securable communications, such as voice, data, and video, among mobile users to facilitate command and control within, and in support of, tactical forces, and (d) usually requires extremely short installation times, usually on the order of hours, in order to meet the requirements of frequent relocation.
Tactical Data Information Link (TADIL) - A standardized communications link, approved by the Joint Staff, that is suitable for transmission of digital information, and is characterized by standardized message formats and transmission characteristics.
Tactical Data Information Link--A (TADIL--A) - A netted link in which one unit acts as a net control station and interrogates each unit by roll call. Note: Once interrogated, that unit transmits its data to the net. This means that each unit receives all the information transmitted. This is a direct transfer of data and no relaying is involved.
Tactical Data Information Link--B (TADIL--B) - A point-to-point data link between two units which provides for simultaneous transmission and reception of data (duplex).
Tactical Load - For the host service tactical forces, the total power requirements for communications, including the requirements for weapons, detection, command and control systems, and related support functions. Note: The tactical load is a part of the operational load.
TADIL - Acronym for tactical data information link.
TADSS - Acronym for Tactical Automatic Digital Switching System.
Tagged Image File Format (TIFF) - A file format used to store an image using the particular data structure of the file.
TAI - Abbreviation for International Atomic Time.
Tail Circuit - 1. A circuit which connects the serial lines of two modems together. 2. A communications line from the end of a major transmission link, such as a microwave link, satellite link, or LAN, to the end-user location. Note: A tail circuit is a part of a user-to-user connection.
Tailgate - To gain unauthorized physical access by following an authorized person through a controlled door.
Tailing - In facsimile systems, the excessive prolongation of the decay of the signal. Synonym hangover.
Take - See clip. 1. In moving picture or television technology, a relatively short, continuous set of frames (often including the associated audio, if any), stored on a recording medium. Synonyms clip, scene. 2. In audio, a short, uninterrupted sound track. Note: Both audio and video clips may be part of a digitized information package, e.g., on a Web page. 3. To limit to a predetermined level (e.g., at the output of an otherwise linear amplifier) the amplitude of an otherwise linear signal. Note: In contrast with an analog compression circuit, which reduces the dynamic range of a signal but retains its basic waveform, a clipping circuit treats (processes, amplifies) a signal in a linear fashion unless the output level reaches a certain threshold, which it may not exceed, and at which it remains unless the input decreases to a level at which the processed output level is lower than the clipping level.
Takeoff Angle - Synonym departure angle. - The angle between the axis of the main lobe of an antenna pattern and the horizontal plane at the transmitting antenna.
Tampering - 1. Penetration or modification of internal operations, or the insertion of active or passive tapping mechanisms, to determine the nature of, or monitor or record , e.g., secret data. 2. Unauthorized modification altering the proper functioning of INFOSEC equipment. 3. Unauthorized modification of sensitive systems or sensitive information.
Tandem - 1. Pertaining to an arrangement or sequencing of networks, circuits, or links, in which the output terminals of one network, circuit, or link are connected directly to the input terminals of another network, circuit, or link. Note: For example, concatenated microwave links constitute a tandem connection. 2. A switching system in the message network that establishes trunk-to-trunk connections. Tandems may be further identified as local tandems, LATA tandems, or access tandems.
Tandem Area - The general areas served by the local offices having direct trunks to or from the tandem office. This area may consist of one or more communities or may include only a portion of a relatively large city.
Tandem Center - In a switched public telecommunications network, a facility that connects trunks to trunks and does not connect any local loops.
Tandem Circuit - A general classification of circuits or trunks between a tandem central office unit and any other central office or switchboard. Synonym tandem trunk.
Tandem Connection - A call switched at a tandem office.
Tandem Office - A central office unit used primarily as an intermediate switching point for traffic between local central offices within the tandem area. Where qualified by a modifying expression, or other explanation, this term may be applied to an office employed for both the interconnection of local central offices within the tandem area and for the interconnection of these local offices with other central offices, e.g., long haul tandem office.
Tandem Signaling - One of the most difficult conditions for speech coders to perfom well in is the case where a digital speech-coded signal is transmitted from the mobile to the base station, and then demodolated into an analog signal which is then speech coded for retransmission as a digital signal over a landline or wireless link. This situation, called tandem signaling, tends to exaggerate the bit errors originally received at the base station. Tandem signaling is difficult to protect against, but is an important evaluation criterion in the evaluation of speech coders. As wireless systems proliferate, there will be a greater demand for mobile-to-mobile communications, and such links will, by definition, involve at least two independent, noisy tandems.
Tandem Tie Trunk Network (TTTN) - An arrangement that permits sequential connection of tie trunks between PBX and Centrex® locations by using tandem operation. Note: Tandem operation permits two or more dial tie trunks to be connected at a tandem center to form a through connection.
Tandem Trunk - Synonym tandem circuit. - A general classification of circuits or trunks between a tandem central office unit and any other central office or switchboard.
Tap - 1. To draw energy from a circuit. 2. To monitor, with or without authorization, the information that is being transmitted via a communications circuit. 3. To extract a portion of the signal from an optical fiber or communications link. Note: One method of tapping an optical fiber is to bend it to a relatively short radius, thus promoting radiation of a portion of the optical signal.
Tapered Fiber - An optical fiber in which the cross section, i.e., cross-sectional diameter or area, varies, i.e., increases or decreases, monotonically with length.
Tape Relay - A method of retransmitting TTY traffic from one channel to another, in which messages arriving on an incoming channel are recorded in the form of perforated tape, this tape then being either fed directly and automatically into an outgoing channel, or manually transferred to an automatic transmitter for transmission on an outgoing channel.
Target Language - In computing, data processing, and communications systems, a language into which statements are translated. Note: Translators, assemblers, and compilers prepare target language programs, usually machine-language programs, from source language programs, usually high-level language programs written by programmers.
Tariff - Documents filed by a telephone company with a state public utility commission and the FCC describing its services and the payments to be charged for the services. The published schedule of rates or charges for a specific unit of equipment, facility, or type of service such as might be provided by a telecommunications common carrier.
TASI - Acronym for time-assignment speech interpolation.
TAT - Abbreviation for transatlantic telecommunications (cable). Note: TAT formerly stood for transatlantic telephone (cable).
T-carrier - In telecommunications, T-carrier is the generic designator for any of several digitally multiplexed telecommunications carrier systems originally developed by Bell Labs and used in North America and Japan. The basic unit of the T-carrier system is the DS0, which has a transmission rate of 64 kbit/s, and is commonly used for one voice circuit. Note 1: The designators for T-carrier in the North American digital hierarchy correspond to the designators for the digital signal (DS) level hierarchy. See the associated table below. Note 2: T-carrier systems were originally designed to transmit digitized voice signals. Current applications also include digital data transmission. Note 3: If an "F" precedes the "T", a fiber optic cable system is indicated at the same rates. Note 4: The table below lists the designators and rates for current T-Carrier systems. Note 5: The North American and Japanese hierarchies are based on multiplexing 24 voice-frequency channels and multiples thereof, whereas the European hierarchy is based on multiplexing 30 voice-frequency channels and multiples thereof.
The E-carrier system, where 'E' stands for European, is incompatible with the T-carrier and is used just about everywhere else in the world besides North America and Japan. It typically uses the E1 line rate and the E3 line rate. The E2 line rate is less commonly used.
TCB - Abbreviation for trusted computing base. - [The] totality of protection mechanisms within a computer system, including hardware, firmware, and software, the combination of which is responsible for enforcing a security policy. Note: The ability of a trusted computing base to enforce correctly a unified security policy depends on the correctness of the mechanisms within the trusted computing base, the protection of those mechanisms to ensure their correctness, and the correct input of parameters related to the security policy.
TCF - Abbreviation for technical control facility. - A physical plant, or a designated and specially configured part thereof, that (a) contains the equipment necessary for ensuring fast, reliable, and secure exchange of information, (b) typically includes distribution frames and associated panels, jacks, and switches and monitoring, test, conditioning, and orderwire equipment, and (c) allows telecommunications systems control personnel to exercise operational control of communications paths and facilities, make quality analyses of communications and communications channels, monitor operations and maintenance functions, recognize and correct deteriorating conditions, restore disrupted communications, provide requested on-call circuits, and take or direct such actions as may be required and practical to provide effective telecommunications services.
T-Coupler - A passive optical coupler having three ports (three fibers). Note 1: Two isolated inputs may be combined into one output; or one input, into two isolated outputs. Note 2: The amount of coupling loss, usually expressed in dB, between ports is determined by the design and construction of the coupler. [After FAA] Synonyms directional coupler, splitter, tee coupler.
TCP - Abbreviation for Transmission Control Protocol. In the Internet Protocol suite, a standard, connection-oriented, full-duplex, host-to-host protocol used over packet-switched computer communications networks. Note 1: TCP corresponds closely to the ISO Open Systems Interconnection--Reference Model (OSI--RM) Layer 4 (Transport Layer). Note 2: The OSI--RM uses TP-0 or TP-4 protocols for transmission control. See Transmission Control Protocol/Internet Protocol
TCP/IP - Abbreviation for Transmission Control Protocol / Internet Protocol. Two interrelated protocols that are part of the Internet protocol suite. Note 1: TCP operates on the OSI Transport Layer and breaks data into packets. IP operates on the OSI Network Layer and routes packets. Note 2: TCP/IP was originally developed by the U.S. Department of Defense.
TCP/IP Suite - The suite of interrelated protocols associated with Transmission Control Protocol / Internet Protocol. Note 1: The TCP/IP Suite includes, but is not limited to, protocols such as TCP, IP, UDP, ICMP, FTP, and SMTP. Note 2: Additional application and management protocols are sometimes considered part of the TCP/IP Suite. This includes protocols such as SNMP.
TCS - Abbreviation for trusted computer system. 1. [An] information system (IS) employing sufficient hardware and software assurance measures to allow simultaneous processing of a range of classified or sensitive information. 2. A data processing system that provides sufficient computer security to allow for concurrent access to data by users with different access rights and to data with different security classification and security categories.
TCU - Abbreviation for teletypewriter control unit. - A device that controls and coordinates operations between teletypewriters and message switching centers.
TDD - Abbreviation for Telecommunications Device for the Deaf. - A machine that uses typed input and output, usually with a visual text display, to enable individuals with hearing or speech impairments to communicate over a telecommunications network.
TDEA Decryption Operation - the transformation of a 64-bit block I into a 64-bit block O that is defined as follows: O = DK1(EK2(DK3(I))). The standard specifies the following keying options for bundle (K1, K2, K3)
- Keying Option 1 - K1, K2, and K3 are independent keys;
- Keying Option 2 - K1 and K2 are independent keys and K3 = K1;
- Keying Option 3 - K1 = K2 = K3.
TDM - Abbreviation for time-division multiplexing. - 1. Digital multiplexing in which two or more apparently simultaneous channels are derived from a given frequency spectrum, i.e., bit stream, by interleaving pulses representing bits from different channels. Note: Successive pulses represent bits from successive channels, e.g., voice channels in a T1 system. 2. A multiplexing technique whereby two or more channels are derived from a transmission mediuim by dividing access to the medium into sequential intervals. Each channel has access to the entire bandwidth of the medium during its interval. This implies that one transmitter uses one channel to send several bit streams of information.
TDMA - Abbreviation for time-division multiple access. - 1. A communications technique that uses a common channel (multipoint or broadcast) for communications among multiple users by allocating unique time slots to different users. Note: TDMA is used extensively in satellite systems, local area networks, physical security systems, and combat-net radio systems. 2. A multiple access technique whereby users share a transmission medium by being assigned and using (one at a time) for a limited number of time division multiplexed channels; implies that several transmitters use one channel for sending several bit streams.
TE - Abbreviation for transverse electric. See transverse electric mode. A mode whose electric field vector is normal to the direction of propagation. Note: TE modes may be useful modes in waveguides. In an optical fiber, TE and TM modes correspond to meridional rays.
Technical Area - In the military community, an area in which temperature, humidity, or access is controlled because it contains equipment, such as communications, computing, control, or support equipment, that requires such controls.
Technical Control Facility (TCF) - A physical plant, or a designated and specially configured part thereof, that (a) contains the equipment necessary for ensuring fast, reliable, and secure exchange of information, (b) typically includes distribution frames and associated panels, jacks, and switches and monitoring, test, conditioning, and orderwire equipment, and (c) allows telecommunications systems control personnel to exercise operational control of communications paths and facilities, make quality analyses of communications and communications channels, monitor operations and maintenance functions, recognize and correct deteriorating conditions, restore disrupted communications, provide requested on-call circuits, and take or direct such actions as may be required and practical to provide effective telecommunications services.
Technical Control Hubbing Repeater - Synonym data conferencing repeater. - A device that enables any one user of a group of users to transmit a message to all other users in that group.
Technical Load - The portion of the operational load required for communications, tactical operations, and ancillary equipment including necessary lighting, air-conditioning, or ventilation required for full continuity of communications.
Technical Vulnerability - In information handling, a hardware, software, or firmware weakness, or design deficiency, that leaves a system open to assault, harm, or unauthorized exploitation, either externally or internally, thereby resulting in unacceptable risk of information compromise, information alteration, or service denial.
TED - Abbreviation for trunk encryption device. - A bulk encryption device used to provide secure communications over a wideband digital transmission link. Note: A TED is usually located between the output of a trunk group multiplexer and a wideband radio or cable facility.
Tee Coupler - A passive coupler that has three ports. Synonyms directional coupler, splitter, T-coupler.
TEK - Abbreviation for traffic encryption key. - [A] key used to encrypt plain text or to superencrypt previously encrypted text and/or to decrypt cipher text.
Teleaction Service - In Integrated Services Digital Network (ISDN) applications, a telecommunications service that uses very short messages with very low data transmission rates between the user and the network.
Telecommand - The use of telecommunication for the transmission of signals to initiate, modify or terminate functions of equipment at a distance.
Telecommunication - 1. Any transmission, emission, or reception of signs, signals, writing, images and sounds or intelligence of any nature by wire, radio, optical or other electromagnetic systems. 2. Any transmission, emission, or reception of signs, signals, writings, images, sounds, or information of any nature by wire, radio, visual, or other electromagnetic systems.
Telecommunication Administration - An administration, or the part of a combined postal and telecommunication administration, concerned with the provision of telecommunication service.
Telecommunication Architecture - See network architecture. - 1. The design principles, physical configuration, functional organization, operational procedures, and data formats used as the bases for the design, construction, modification, and operation of a communications network. 2. The structure of an existing communications network, including the physical configuration, facilities, operational structure, operational procedures, and the data formats in use.
Telecommunications - Telecommunications is any process that enables one or more users to pass to one or more other users information of any nature delivered in any usable form, by wire, radio, visual, or other electrical, electromagnetic, optical means. The word is derived from the Greek tele, "far off," and the Latin communicare "to share."
Telecommunications Center - See communications center. - 1. An agency charged with the responsibility for handling and controlling communications traffic. The center normally includes message center, transmitting, and receiving facilities. 2. A facility that (a) serves as a node for a communications network, (b) is equipped for technical control and maintenance of the circuits originating, transiting, or terminating at the node, (c) may contain message-center facilities, and (d) may serve as a gateway.
Telecommunications Closet - In a premises distribution system, a telecommunications closet is an area for connecting the horizontal and backbone wiring and for containing active or passive PDS equipment.
Telecommunications Device for the Deaf (TDD) - A machine that uses typed input and output, usually with a visual text display, to enable individuals with hearing or speech impairments to communicate over a telecommunications network.
Telecommunication Sector - The sector that includes the telecommunications service providers, network operators, regulators, manufacturers, subscribers, and users.
Telecommunications Facilities - The aggregate of equipment, such as radios, telephones, teletypewriters, facsimile equipment, data equipment, cables, and switches, used for providing telecommunications services.
Telecommunications Infrastructure - The organizations, personnel, procedures, facilities, and networks employed to transmit and receive information by electrical or electronic means. Note 1: Telecommunications facilities include, but are not necessarily limited to, terrestrial radio, metallic and optical fiber cables, artificial Earth satellite communications, radio and television stations (traditional broadcast as well as cable and satellite broadcast), public switched telephone network (s), etc. Note 2: Examples of advanced telecommunications infrastructure facilities are direct broadcast satellite (DBS), digital audio broadcasting (DAB), Advanced Digital Television, and the Global Positioning System (GPS), which is used extensively for precise navigation and timing.
Telecommunications Link - A communications facility or channel, including feeder and local distribution plant, having a termination in a center in the telecommunications network. Examples of such a link include (but are not necessarily restricted to): optical-fiber cable, coaxial cable, metallic cables, transmitting and receiving antenna.
Telecommunications Load Equipment - Equipment powered from a primary or secondary distribution of a centralized dc power system owned or operated by exchange and interexchange carriers.
Telecommunications Management Network (TMN) - A network that interfaces with a telecommunications network at several points in order to receive information from, and to control the operation of, the telecommunications network. Note: A TMN may use parts of the managed telecommunications network to provide for the TMN communications.
Telecommunications Network - A telecommunications network is a system of interconnected facilities designed to carry traffic from a variety of telecommunications services. The network has two different but related aspects. In terms of its physical components, it is a facilities network. In terms of the variety of telecommunications services that it provides, it can support a set of many traffic networks, each representing a particular interconnection of facilities.
Telecommunications Relay Center Fee/Charge/Surcharge - This state fee helps pay for the relay center that transmits and translates calls for people who are deaf, hard-of-hearing or speech disabled. Mandated nationally by Congress with the passage of the Americans with Disabilities Act, it may also be called “Telecommunication Devices for the Deaf Tax.”
Telecommunications Security - See communications security. Measures and controls taken to deny unauthorized persons information derived from telecommunications and to ensure the authenticity of such telecommunications. Note: Communications security includes cryptosecurity, transmission security, emission security, and physical security of COMSEC material. [INFOSEC]
- (a) cryptosecurity: [The] component of communications security that results from the provision of technically sound cryptosystems and their proper use. [NIS]
- (b) emission security: Protection resulting from all measures taken to deny unauthorized persons information of value which might be derived from intercept and analysis of compromising emanations from crypto-equipment, AIS, and telecommunications systems. [NIS]
- (c) physical security: The component of communications security that results from all physical measures necessary to safeguard classified equipment, material, and documents from access thereto or observation thereof by unauthorized persons. [JP 1-02]
- (d) transmission security: [The] component of communications security that results from the application of measures designed to protect transmissions from interception and exploitation by means other than cryptanalysis.
Telecommunications Service - 1. Any service provided by a telecommunication provider. 2. A specified set of user-information transfer capabilities provided to a group of users by a telecommunications system. Note: The telecommunications service user is responsible for the information content of the message. The telecommunications service provider has the responsibility for the acceptance, transmission, and delivery of the message.
Telecommunications Service Priority (TSP) Service - A regulated service provided by a telecommunications provider, such as an operating telephone company or a carrier, for NS/EP telecommunications. Note: The TSP service replaced Restoration Priority (RP) service effective September 1990.
Telecommunications Service Priority (TSP) System - A system that provides a means for telecommunications users to obtain priority treatment from service providers for the NS/EP telecommunications requirements. Note: The TSP system replaced the Restoration Priority (RP) system effective September 1990.
Telecommunications Service Priority (TSP) System User - Any individual, organization, or activity that interacts with the NS/EP TSP System.
Telecommunications System - See communications system. A collection of individual communications networks, transmission systems, relay stations, tributary stations, and data terminal equipment (DTE) usually capable of interconnection and interoperation to form an integrated whole. Note: The components of a communications system serve a common purpose, are technically compatible, use common procedures, respond to controls, and operate in unison.
Telecommunications System Operator - The organization responsible for providing telecommunications services to users.
Teleconference - The live exchange of information among persons and machines remote from one another but linked by a telecommunications system. Note: The telecommunications system may support the teleconference by providing audio, video, and data services by one or more means, such as telephone, telegraph, teletype, radio, and television.
Telegram - Written matter intended to be transmitted by telegraphy for delivery to the addressee. This term also includes radiotelegrams unless otherwise specified. In this definition the term telegraphy has the same general meaning as defined in the [1979 General Worldwide Administrative Radio Conference] Convention.
Telegraph - See telegraphy. A form of telecommunication which is concerned in any process providing transmission and reproduction at a distance of documentary matter, such as written or printed matter or fixed images, or the reproduction at a distance of any kind of information in such a form. For the purposes of the Radio Regulations, unless otherwise specified therein, telegraphy shall mean a form of telecommunication for the transmission of written matter by the use of a signal code.
Telegraphy - A form of telecommunication which is concerned in any process providing transmission and reproduction at a distance of documentary matter, such as written or printed matter or fixed images, or the reproduction at a distance of any kind of information in such a form. For the purposes of the Radio Regulations, unless otherwise specified therein, telegraphy shall mean a form of telecommunication for the transmission of written matter by the use of a signal code.
Telemeter - A measuring, transmitting, and receiving device used in telemetry. Any scientific instrument for observing events at a distance and transmitting the information back to the observer.
Telemetered, Telemetering, Telemeters - To measure, transmit, and receive (data) automatically from a distant source, as from a spacecraft or an electric power grid.
Telemetry - 1. The use of telecommunication for automatically indicating or recording measurements at a distance from the measuring instrument. 2. The transmission of nonvoice signals for the purpose of automatically indicating or recording measurements at a distance from the measuring instrument.
Telephone - A user end instrument that is used to transmit and receive voice-frequency signals.
Telephone Book - A directory of the names of telephone subscribers with their telephone numbers and often their addresses. A directory containing an alphabetical list of telephone subscribers and their telephone numbers.
Telephone Booth - A small enclosure containing a public telephone. Also a slang term referring to one of the many phone terminals on the floor of the New York Stock Exchange that is used by floor traders to receive orders.
Telephone Exchange - Synonym for central office. A central system of switches and other equipment that establishes connections between individual telephones. Also called switchboard. A workplace that serves as a telecommunications facility where lines from telephones can be connected together to permit communication.
In the field of telecommunications, a telephone exchange (US: telephone switch) is a piece of equipment that connects phone calls. It is what makes your phone calls "work" in the sense of making connections and relaying the speech information.
The term exchange can also be used to refer to an area served by a particular switch. And more narrowly, it can refer to the first three digits of the local number. In the past, the first two or three digits would map to a mnemonic exchange name, e.g. 869–1234 was formerly TOwnsend 9–1234, and before that (in some localities) might have been TOWnsend 1234 (only the capital letters and numbers being dialed). In December of 1930, New York City became the first locality in the United States to adopt the two-letter, five-number format; it remained alone in this respect until after World War II, when other municipalities across the country began to follow suit (in some areas, most notably much of California, telephone numbers in the 1930s and early 1940s consisted of only six digits, two letters which began the exchange name followed by four numbers, as in DUnkirk 0799).
Prior to the mid-1950s, the number immediately following the name could never be a "0" or "1;" indeed, "0" was never pressed into service at all, except in the immediate Los Angeles area (the "BEnsonhurst 0" exchange mentioned in an episode of the popular TV sitcom The Honeymooners was fictitious). In 1955, the Bell System attempted to standardize the process of naming exchanges by issuing a "recommended list" of names to be used for the various number combinations. In 1961, New York Telephone introduced "selected-letter" exchanges, in which the two letters did not mark the start of any particular name (example: FL 6-9970), and by 1965 all newly-connected phone numbers nationwide consisted of numerals only (Wichita Falls, Texas had been the first locality in the United States to implement the latter, having done so in 1958; meanwhile, pre-existing numbers continued to be displayed the old way in many places well into the 1970s). The United Kingdom never adopted the two-letter, five-number format, remaining with the three-letter, four-number format until converting to all-numeric phone numbers in 1968.
In the United States, the word exchange can also have the technical meaning of a local access and transport area under the Modification of Final Judgment (MFJ).
Telephone Jack - In the U. S., telephone jacks are also known as registered jacks, sometimes described as RJ-XX, and are a series of telephone connection interfaces (receptacle and plug) that are registered with the U.S. Federal Communications Commission (FCC). They derive from interfaces that were part of AT&T's Universal Service Order Codes (USOC) and were adopted as part of FCC regulations (specifically Part 68, Subpart F. Section 68.502). The term jack sometimes means both receptacle and plug and sometimes just the receptacle.
RJ-11
The most common telephone jack is the RJ-11 jack, which can have six conductors but usually is implemented with four. The RJ-11 jack is likely to be the jack that your household or office phones are plugged into from the ordinary "untwisted" wire (sometimes called "gray satin" or "flat wire") people are most familiar with. In turn, the jacks connect to the "outside" longer wires known as twisted pair that connect to the telephone company central office or to a private branch exchange (PBX).The four wires are usually characterized as a red and green pair and a black and white pair. The red and green pair typically carry voice or data. On an outside phone company connection, the black and white pair may be used for low-voltage signals such as phone lights. On a PBX system, they may be used for other kinds of signaling.
A computer that uses a dial-up modem to connect to a network is usually plugged into an RJ-11 jack.
RJ-14
The RJ-14 is similar to the RJ-11, but the four wires are used for two phone lines. Typically, one set of wires (for one line) contains a red wire and a green wire. The other set contains a yellow and black wire. Each set carries one analog "conversation" (voice or data).RJ-45
The RJ-45 is a single-line jack for digital transmission over ordinary phone wire, either untwisted or twisted. The interface has eight pins or positions. For connecting a modem, printer, or a data PBX at a data rate up to 19.2 Kbps, you can use untwisted wire. For faster transmissions in which you're connecting to an Ethernet 10BASET network, you need to use twisted pair wire. (Untwisted is usually a flat wire like common household phone extension wire. Twisted is often round.)There are two varieties of RJ-45: keyed and unkeyed. Keyed has a small bump on its end and the female complements it. Both jack and plug must match.
Telephone Line Sharing - A technology that allows a single phone line to share incoming and outgoing access for multiple devices. Typically Telephone Line Sharing Technology allows voice (phones and answering machine) and a fax machine or fax modem to operate on a shared phone line. Other applications include any variation of voice, a fax machine, fax/modem and/or modem(s).
Incoming calls are automatically routed to the proper device(s). If the call comes in and it is a fax call, the call is automatically routed to the fax machine or fax modem. If the call is a modem call, it is routed to the correct modem. Voice calls are routes to phone(s) and/or answering machine. May require a security access code (SAC) in the dialing string to automatically switch to the modem.
Since the need for to subscribe to a separate "fax line" from the local telephone company is eliminated, the return on investment (ROI) is very high. The initial cost of the device is returned in savings in a few months. After that you will save the monthly bills associated with fax, data or voice lines. For almost every business, a telephone line sharing technology is a smart investment.
Telephone Network - The system of wires, fiber-optic cables, satellites and transmission towers that transmit telephone messages from caller to receiver.
Telephone Number - The unique network address that is assigned to a telephone user, i.e., subscriber, for routing telephone calls.
Telephone Switch - A large-scale computer used to route telephone calls in a central office. Such devices are made by Lucent, Nortel and others.
Telephone Tag - A series of unsuccessful calls exchanged by two people who are attempting to contact each other by telephone.
Telephonic - 1. Of or relating to telephones. 2. Transmitted or conveyed by telephone.
Telephony - 1. The branch of science devoted to the transmission, reception, and reproduction of sounds, such as speech and tones that represent digits for signaling. Note 1: Transmission may be via various media, such as wire, optical fibers, or radio. Note 2: Analog representations of sounds may be digitized, transmitted, and, on reception, converted back to analog form. Note 3: "Telephony" originally entailed only the transmission of voice and voice-frequency data. Currently, it includes new services, such as the transmission of graphics information. 2. A form of telecommunication set up for the transmission of speech or, in some cases, other sounds. 3. The technology and manufacture of telephone equipment. 4. The transmission of sound between distant stations, especially by radio or telephone.
Meaning "sound over distance," it refers to electronically transmitting the human voice. In the beginning, telephony dealt only with analog signals in the circuit-switched networks of the telephone companies. It later referred to a mix of analog and digital circuits, but still with the telephone industry. Starting in the 1990s, telephony began to embrace sending voice over IP (VoIP) networks, which is now deployed by common carriers, private enterprises and independent VoIP providers.
Telephoto - 1. Of or relating to a photographic lens or lens system used to produce a large image of a distant object. 2. Of or relating to an instrument that electrically transmits photographs. 3. Pertaining to pictures transmitted via a telecommunications system.
Telephotograph - 1. A telephoto. 2. A photograph transmitted and reproduced over a distance.
Telephotography - 1. The process or technique of photographing distant objects, using a telephoto lens on a camera. 2. The technique or process of transmitting charts, pictures, and photographs over a distance.
Teleprinter - A typewriter-like terminal with a keyboard and built-in printer. It can be a desktop or portable unit. Teleprinters were quite common years ago as input terminals for computers, but have given way to the video screen. Teleprinter-like devices are still used in retail applications where receipts are necessary.
Teleprinters were widely used starting with the very first computers. They lived well into the 1970s as a computer input device. Any keyboard and printing unit can be called a teleprinter.
Paper tape was widely used on teleprinters to record incoming data. The reel of tape in this picture is on the lower left side of the unit. (Image courtesy of General Electric Company.)
A teletypewriter that can only receive data and does not have a keyboard for transmission.
Teleprocessing - The combining of telecommunications and computer operations interacting in the automatic processing, reception, and transmission of data and/or information. [JP 1-02] Note: Teleprocessing includes human-machine interface equipment.
Teleran - An air-traffic control system in which the image of a ground-based radar unit is televised to aircraft in the vicinity so that pilots may see their positions in relation to other aircraft.
Teletext - An electronic communications system in which printed information is broadcast by television signal to sets equipped with decoders. An international store-and-forward essentially error-free communications service that is defined by the CCITT (now the ITU-T), has a data signaling rate (DSR) of 2400 b/s over switched telephone networks, and has a communications protocol that supports the CCITT Group 4 facsimile service.
Teletraining - Training that (a) in which usually live instruction is conveyed in real time via telecommunications facilities, (b) that may be accomplished on a point-to-point basis or on a point-to-multipoint basis, and (c) may assume many forms, such as a teleseminar, a teleconference, or an electronic classroom, usually including both audio and video. Synonyms distance learning, distance training, electronic classroom, virtual instruction.
Teletype - A trademark used for a teletypewriter.
Teletypewriter (TTY) - A printing telegraph instrument that has a signal-actuated mechanism for automatically printing received messages. An electromechanical typewriter that either transmits or receives messages coded in electrical signals carried by telegraph or telephone wires. Note 1: A TTY may have a keyboard similar to that of a typewriter for sending messages. Note 2: Radio circuits carrying TTY traffic are called "RTTY circuits" or "RATT circuits."
Teletypewriter Control Unit (TCU) - A device that controls and coordinates operations between teletypewriters and message switching centers.
Teletypewriter Exchange Service (TWX) - A switched teletypewriter service in which suitably arranged teletypewriter stations are provided with lines to a central office for access to other such stations.
Teletypewriter Signal Distortion - The shifting of signal pulse transitions from their proper positions relative to the beginning of the start pulse. Note: The magnitude of the distortion is expressed in percent of a perfect unit pulse length. Synonym start-stop TTY distortion.
Television (TV) - A form of telecommunication for the transmission of transient images of fixed or moving objects.Note 1: The picture signal is usually accompanied by the sound signal. Note 2: In North America, TV signals are generated, transmitted, received, and displayed in accordance with the NTSC standard.
Telex - 1. A communications system consisting of teletypewriters connected to a telephonic network (automatic exchanges) to send and receive signals. 2. A message sent or received by such a system.
(TELetypewriter EXchange) An international, dial-up data communications service administered in the U.S. by AT&T, MCI and other providers. Developed in the U.S. and other European countries in the 1930s, it was the first data communications service that used typewriter-like terminals (teletypewriters). Prior to Telex, telegrams and cablegrams were the primary method for delivering a text message. By the 1960s, Telex became a worldwide, realtime, data communications service. Although diminishing each year, Telex is still used for commerce in more than 200 countries.
Telex started out transmitting Baudot code at 50 bps. Although upgraded, it is still a low-speed data service. It was originally administered worldwide by various carriers and the local PTTs. Western Union handled the U.S., and in 1971, purchased and integrated the Bell System's TWX service. AT&T acquired Western Union's Telex service in 1991.
Telex Machine - A character printer connected to a telegraph that operates like a typewriter
Telnet - A program that allows Internet users to login to computers other than their host. Telnet also refers to the act of doing so. The TCP/IP standard network virtual terminal protocol that is used for remote terminal connection service and that allows a user at one site to interact with systems at other sites as if that user terminal were directly connected to computers at those sites.
TEM - Abbreviation for transverse electric and magnetic mode. - A mode whose electric and magnetic field vectors are both normal to the direction of propagation. Note: The TEM mode is the most useful mode in a coaxial cable.
TEMPEST - 1. [A] Short name referring to investigation, study, and control of compromising emanations from information systems (IS) equipment. 2. To shield against compromising emanations.
Temporal Application - A video application requiring high temporal resolution, i.e., reduced jerkiness, possibly at the expense of reduced spatial resolution. Note: An example of temporal applications is the ability to accurately discern moving image features such as facial expressions and lip movements.
Temporal Edge Noise - In a video display, that form of edge busyness that is characterized by time-varying sharpness at the edges of objects.
Terminal - A device capable of sending, receiving, or sending and receiving information over a communications channel.
Terminal Access Controller (TAC) - A host computer that accepts terminal connections, usually from dial-up lines, and that allows the user to invoke Internet remote log-on procedures, such as Telnet.
Terminal Adapter - An interfacing device employed at the "R" reference point in an ISDN environment that allows connection of a non-ISDN terminal at the physical layer to communicate with an ISDN network. Note: Typically, a terminal adapter will support standard RJ-11 telephone connection plugs for voice and RS-232C, V.35 and RS-449 interfaces for data.
Terminal Data - Data maintained for each terminal including the current terminal location (and capabilities).
Terminal Deregistration - The process by which a wireless terminal's previous location registration is canceled.
Terminal Endpoint (TE) Functional Group - A functional group that includes functions broadly belonging to Layer 1 and higher layers of the ITU-T Recommendation X.200 Reference Model. Note 1: The functions of a TE functional group are performed on various types of equipment, or combinations of equipment, such as digital telephones, data terminal equipment, and/or integrated work stations. Note 2: Examples of TE functions are protocol-handling, maintenance, interface, and connection functions.
Terminal Equipment - 1. Communications equipment at either end of a communications link, used to permit the stations involved to accomplish the mission for which the link was established. 2. In radio-relay systems, equipment used at points where data are inserted or derived, as distinct from equipment used only to relay a reconstituted signal. 3. Telephone and telegraph switchboards and other centrally located equipment at which communications circuits are terminated. 4. Equipment that originates or terminates signals at the specified rate.
Terminal Identifier - A code identifying a specific terminal.Terminal Impedance - 1. The impedance as measured at the unloaded output terminals of transmission equipment or a line that is otherwise in normal operating condition. 2. The ratio of voltage to current at the output terminals of a device, including the connected load.
Terminal Mobility - In commercial wireless networks, the ability of a terminal, while in motion, to access telecommunication services from different locations, and the capability of the network to identify and locate that terminal.
Terminal Mobility Controller - A device that provides the control logic for terminal authentication, location management, alerting, and routing to radio personal terminal / radio terminations (RPT/RTs).
Terminal Mobility Management - In personal communications service (PCS), (a) providing authentication of terminal information, (b) maintaining terminal location and capability information for each terminal, and (c) providing translation between terminal identification and location (routing address) for the completion of calls to terminals.
Terminal Registration - The process of associating a terminal with a terminal registration area.
Terminal Registration Area - A territory in which a wireless terminal is registered for terminal mobility.
Terminal Service Profile (TSP) - Information that the service provider maintains for a given user to characterize the services offered by the network to that user. A TSP may be allocated to an interface or to a particular user equipment or a group of user equipment.
Terminal Type - The variety of terminal or the originator (e.g., dual-tone multifrequency (DTMF) phone, ISDN terminal).
Terminating Endpoint - In a wideband packet node, the part of the node that receives packetized traffic, depacketizes it, and then plays it back as channelized traffic.
Terminating Network Function - Of a UPT call, any network function associated with the termination of the call to the destination terminal.
Termination - 1. The load connected to a transmission line, circuit, or device. Note: For a uniform transmission line, if the termination impedance is equal to the characteristic impedance of the line, wave reflections from the end of the line will be avoided. 2. In hollow metallic waveguides, the point at which energy propagating in the waveguide continues in a nonwaveguide propagation mode into a load. 3. An impedance, often resistive, that is connected to a transmission line or piece of equipment as a dummy load, for test purposes.
Terminus - A device used to terminate, position, and hold an optical fiber within a connector.
Ternary Signal - A signal that can assume, at any given instant, one of three significant conditions, such as power level, phase position, pulse duration, or frequency. Note: Examples of ternary signals are (a) a pulse that can have a positive, zero, or negative voltage value at any given instant, (b) a sine wave that can assume phases of 0°, 120°, or 240° relative to a clock pulse, and (c) a carrier wave that can assume any one of three different frequencies depending on three different modulation signal significant conditions.
Terrestrial Microwave Radio - Terrestrial microwave radio is a transmission systems consisting of at least two radio transmitter/receivers (transceivers) connected to high gain antennas (directional antennas which concentrate electromagnetic or radiowave energy in narrow beams) focused in pairs on each other. The operation is point-to-point, that is, communications are established between two and only two antennas (installations) with line-of-sight visibility. This can be contrasted to point-to- multipoint systems like broadcast radio or television.
Terrestrial Radiocommunication - Any radiocommunication other than space radiocommunication or radio astronomy.
Terrestrial Station - A station effecting terrestrial radiocommunication. In these [Radio] Regulations, unless otherwise stated, any station is a terrestrial station.
Test and Validation - Physical measurements taken (a) to verify conclusions obtained from mathematical modeling and analysis or (b) for the purpose of developing mathematical models.
Test Antenna - An antenna of known performance characteristics used in determining transmission characteristics of equipment and associated propagation paths.
Test Key - Key intended for testing of COMSEC equipment or systems.
Test Point - A point within a piece of equipment or an equipment string that provides access to signals for the purpose of fault isolation.
Test Tone - A tone sent at a predetermined level and frequency through a transmission system for test purposes, such as for facilitating measurements and for aligning gains and losses in the system.
Text Format vs. HTML Format - Some Web applications, such as e-mail or Web pages, can either be viewed in Text or HTML formats. Text formats generally display only the words (text) in an e-mail or on a Web page and not graphics, such as artwork or photos. HTML format allows display of both text and graphics.
TGM - Abbreviation for trunk group multiplexer.
THD - Abbreviation for total harmonic distortion. - Of a signal, the ratio of (a) the sum of the powers of all harmonic frequencies above the fundamental frequency to (b) the power of the fundamental frequency. Note 1: The THD is usually expressed in dB. Note 2: Measurements for calculating the THD are made at the output of a device under specified conditions.
Thermal Noise: The noise generated by thermal agitation of electrons in a conductor. The noise power, P, in watts, is given by P = kT
f, where k is Boltzmann's constant in joules per kelvin, T is the conductor temperature in kelvins, and
Thermal Radiation - 1. Electromagnetic radiations emitted from a heat or light source as a consequence of its temperature; it consists essentially of ultraviolet, visible, and infrared radiations. [JP1] 2. The heat and light produced by a nuclear explosion.
Thermodynamic Temperature - A measure, in kelvins (K), proportional to the thermal energy of a given body at equilibrium. Note 1: A temperature of 0 K is called "absolute zero," and coincides with the minimum molecular activity (i.e., thermal energy) of matter. Note 2: Thermodynamic temperature was formerly called "absolute temperature." Note 3: In practice, the International Temperature Scale of 1990 (ITS-90) serves as the basis for high-accuracy temperature measurements in science and technology.
The Stick - Business quality Single Line Automatic Call Processor. Line sharing device for small or home business as well large corporations and organizations. Automatically routes calls to the assigned device. The Stick allows up to three telecommunication devices plus an answering machine to share one single phone line. This is our most popular fax switch. For more information: The Stick brochure , The Stick online manual.
THF - Abbreviation for tremendously high frequency. See electromagnetic spectrum.
Thin Client (computing) - A server-centric computing model in which the application software, data, and CPU power resides on a network server rather than on the client computer (s). Note 1: This computing philosophy allows administrators to purchase one relatively powerful and expensive server and be confident that any external terminal, regardless of its power or sophistication, can run applications on the server. Most "shopping" Web pages, for example, are thin-client applications (i.e., the client needs nothing more than a browser and a connection to the network to be able to search the "shopping" page and to order products). Local area networks can use thin-client modeling to install only one copy of necessary programs onto the main server for many clients on the network to use. Note 2: Server software is required to interface clients with the software on the server. Synonyms Internet appliance (computing), Internet box (computing), network computer.
Thin-Client Software - Computer programs that reside on a server and react to external requests from a client. Note: This is in contrast to software that is installed on each client computer in a network. Software that resides only on a single server can be maintained and updated with minimal effort.
Thin-Film Laser - A laser that is constructed by thin-film deposition techniques on a substrate for use as a light source, is usually used to drive thin-film optical waveguides, and may be used in integrated optical circuits.
Thin-Film Optical Modulator - A modulator that consists of multilayered films of material of different optical characteristics, is capable of modulating transmitted light by using electro-optic, electro-acoustic, or magneto-optic effects to obtain signal modulation, and may be used as a component in integrated optical circuits.
Thin-Film Optical Multiplexer - A multiplexer that consists of multilayered films of material of different optical characteristics, is capable of multiplexing transmitted light by using electro-optic, electro-acoustic, or magneto-optic effects to obtain signal multiplexing, and may be used as a component in integrated optical circuits.
Thin-Film Optical Switch - A switch that consists of multilayered films of material of different optical characteristics, that is capable of switching transmitted light by using electro-optic, electro-acoustic, or magneto-optic effects to obtain signal switching, and is usually used as a component in integrated optical circuits. Note: Thin-film optical switches may support only one propagation mode.
Thin-Film Optical Waveguide - A slab-dielectric waveguide that consists of multilayered films of material of different optical characteristics, is capable of guiding an optical signal, and may be used as a component in integrated optical circuits.
Third-Order Intercept Point - A point (a) that is an extrapolated convergence--not directly measurable--of intermodulation distortion products in the desired output and (b) that indicates how well a receiver performs in the presence of strong nearby signals. Note: Determination of a third-order intercept point is accomplished by using two test frequencies that fall within the first intermediate frequency mixer passband. Usually, the test frequencies are about 20 to 30 kHz apart.
Third Window - Of silica-based optical fibers, the transmission window at approximately 1.55 m. Note: The third window is the minimum-loss window in silica-based fibers.
Thread - In computer conferencing, a set of sequential messages containing closely related information.
Threat - 1. Capabilities, intentions, and attack methods of adversaries to exploit, or any circumstance or event with the potential to cause harm to, information or an information system. [NIS] 2. Any circumstance or event with the potential to harm an information system (IS) through unauthorized access, destruction, disclosure, modification of data, and/or denial of service.
Threat Analysis - Examination of information to identify the elements comprising a threat.
Threat Assessment - [A] formal description and evaluation of threat to an information system (IS).
Three-Way Calling - A switching system service feature that permits users to add a third party to an established connection at a different number during a call, without the assistance of an attendant or operator.
Allows you to speak to two separate people at the same time. To use, start by placing a call to the first
person. Once that person is on the line, press the switch hook or “flash” button briefly. This places the
first party on hold and gives you a dial tone to reach the second person. Then dial the second number.
Once the second person answers press the switch hook to connect everyone.Threshold - 1. The minimum value of a signal that can be detected by the system or sensor under consideration. 2. A value used to denote predetermined levels, such as those pertaining to volume of message storage, i.e., in-transit storage or queue storage, used in a message switching center. 3. The minimum value of the parameter used to activate a device. 4. The minimum value a stimulus may have to create a desired effect.
Threshold Current - In a laser, the driving current corresponding to lasing threshold.
Threshold Extension - See FM threshold extension. - A change in the value of the FM threshold of a receiver. Note: FM threshold extension may be obtained by decreasing the operational bandwidth, thus decreasing the received noise power and allowing the threshold of the desired signal to occur at a lower signal input level.
Threshold Frequency - In opto-electronics, the frequency of incident radiant energy below which there is no photo-emissive effect.
Through Group - A group of 12 voice-frequency channels transmitted as a unit through a carrier system.
Through-Group Equipment - In carrier telephone transmission, equipment that accepts the signal from a group receiver output and attenuates it to the proper signal level for insertion, without frequency translation, at the input of a group transmitter.
Throughput - 1. The number of bits, characters, or blocks passing through a data communication system, or portion of that system. Note 1: Throughput may vary greatly from its theoretical maximum. Note 2: Throughput is expressed in data units per period of time; e.g., in the DDN, as blocks per second. 2. The maximum capacity of a communications channel or system. 3. A measure of the amount of work performed by a system over a period of time, e.g., the number of jobs per day.
Through Supergroup - An aggregate of 60 voice-frequency channels, i.e., five groups, transmitted as a unit through a carrier system.
Through-Supergroup Equipment - In carrier telephone transmission, equipment that accepts the multiplexed signal from a supergroup receiver output, amplifies it without frequency translation, and provides the proper signal level to the input of a supergroup transmitter equipment.
THz - Abbreviation for terahertz. See electromagnetic spectrum.
TIA - Abbreviation for Telecommunications Industry Association.
Ticket - In computer security, a representation of one or more access rights that a possessor has to an object. Note: The ticket represents an access permission.
Ticketed Call - A call for which a record is made of certain facts concerning the call, such as the time it was placed, the duration, the call originator, call destination numbers, and, where applicable, the attendant's name or initials.
Ticket-Oriented - [In security, a] computer protection system in which each subject maintains a list of unforgeable bit patterns called tickets, one for each object a subject is authorized to access.
TIE - Acronym for time interval error. - 1. The time difference between a real clock and an ideal uniform time scale, after a time interval following perfect synchronization between the clock and the scale. 2. The variation in time delay of a given timing signal with respect to an ideal timing signal over a particular time period.
Tie Trunk - A telephone line that directly connects two private branch exchanges (PBXs).
TIFF (Tag Image File Format) - A common format for exchanging raster graphics (bitmap) images between application programs, including those used for scanner images. A TIFF file can be identified as a file with a ".tiff" or ".tif" file name suffix. The TIFF format was developed in 1986 by an industry committee chaired by the Aldus Corporation (now part of Adobe Software). Microsoft and Hewlett-Packard were among the contributors to the format. One of the most common graphic image formats, TIFF files are commonly used in desktop publishing, faxing, 3-D applications, and medical imaging applications.
TIFF files can be in any of several classes, including gray scale, color palette, or RGB full color, and can include files with JPEG,
LZW , or CCITT Group 4 standard run-length image compression.Time - 1. An epoch, i.e., the designation of an instant on a selected time scale, astronomical or atomic. It is used in the sense of time of day [JP1] 2. On a time scale, the interval between two events, or the duration of an event. 3. An apparently irreversible continuum of ordered events. 4. That which characterizes, or is characterized by, the observed and apparently irreversible continuum of ordered events.
Time Ambiguity - A situation in which more than one different time or time measurement can be obtained under the stated conditions.
Time-Assignment Speech Interpolation (TASI) - An analog technique used on certain long transmission links to increase voice-transmission capacity. Note: TASI works by switching additional users onto any channel temporarily idled because an original user has stopped speaking. When the original user resumes speaking, that user will, in turn, be switched to any channel that happens to be idle.
Time Block - An arbitrary grouping of several consecutive hours of a day, usually for a particular season, during which it is assumed that propagation data are statistically homogeneous.
Time Bomb - 1. In COMSEC, a logic bomb to be activated at a predetermined time. 2. [A] resident computer program that triggers an unauthorized act at a predefined time.
Time Code - A code used for the transmission and identification of time signals. Note: In telecommunications systems, the format of the time code must be specified.
Time Code Ambiguity - The shortest interval between successive repetitions of the same time code value. Note: For example, in a time code in which year-of-century is the most slowly changing field, the time code ambiguity would be 100 years; for a digital clock in which hours and minutes up to a maximum of 11:59 are displayed, the time code ambiguity would be 12 hours.
Time Code Resolution - The interval between two successive time code states. Note: Time code resolution is determined by the most rapidly changing symbol position within the time code. For example, for a digital clock that displays hours and minutes, the time code resolution would be 1 minute.
Time-Consistent Busy Hour (TCBH) - The identical hour each day during which, over a number of days, the highest average traffic is measured.
Time Diversity - Transmission in which signals representing the same information are sent over the same channel at different times. Note: Time diversity is often used over systems subject to burst error conditions, and at intervals adjusted to be longer than an error burst.
Time-Division Multiple Access (TDMA) - 1. A communications technique that uses a common channel (multipoint or broadcast) for communications among multiple users by allocating unique time slots to different users. Note: TDMA is used extensively in satellite systems, local area networks, physical security systems, and combat-net radio systems. 2. A multiple access technique whereby users share a transmission medium by being assigned and using (one at a time) for a limited number of time division multiplexed channels; implies that several transmitters use one channel for sending several bit streams.
Time-Division Multiplexing (TDM) - 1. Digital multiplexing in which two or more apparently simultaneous channels are derived from a given frequency spectrum, i.e., bit stream, by interleaving pulses representing bits from different channels. Note: Successive pulses represent bits from successive channels, e.g., voice channels in a T1 system. 2. A multiplexing technique whereby two or more channels are derived from a transmission mediuim by dividing access to the medium into sequential intervals. Each channel has access to the entire bandwidth of the medium during its interval. This implies that one transmitter uses one channel to send several bit streams of information.
Time Division Switch - A time division switch is a switch that implements the switch matrix using the TDM process, in a time-slot interchange (TSI) arrangement (usually denoted by T in combined time and space division switches).
Time-Division Switching - Switching of time-division multiplexed (TDM) channels by shifting bits between time slots in a TDM frame.
Time-Domain Reflectometer (TDR) - An electronic instrument used to characterize and locate faults in metallic cables (e.g., twisted pair, coax). Note 1: A TDR transmits a fast rise time pulse along the conductor. The resulting reflected pulse is measured at the input as a function of time and displayed on the instrument or plotted, as a function of cable length. Note 2: A TDR may be used to verify cable impedance characteristics, splice and connector location and associated losses, and estimate cable lengths.
Time-Gated Direct-Sequence Spread Spectrum - Direct-sequence spread spectrum where the transmitter is on only for a short fraction of a time interval. The on-time can be periodic or random within a time interval.
Time Guard Band - A time interval left vacant on a channel to provide a margin of safety against intersymbol interference in the time domain between sequential operations, such as detection, integration, differentiation, transmission, encoding, decoding, or switching.
Time Instability - The fluctuation of the time interval error caused by the instability of a real clock.
Time Interval Error (TIE) - 1. The time difference between a real clock and an ideal uniform time scale, after a time interval following perfect synchronization between the clock and the scale. 2. The variation in time delay of a given timing signal with respect to an ideal timing signal over a particular time period.
Time Jitter - Short-term variation or instability in the duration of a specified time interval.
Time Marker - A reference signal, often repeated periodically, enabling the correlation of specific events with a time scale, such as for establishing synchronization.
Time of Occurrence - The date of an event, i.e., the instant an event occurs, with reference to a specified time scale.
Time-Out - 1. A network parameter related to an enforced event designed to occur at the conclusion of a predetermined elapsed time. 2. A specified period of time that will be allowed to elapse in a system before a specified event is to take place, unless another specified event occurs first; in either case, the period is terminated when either event takes place. Note: A time-out condition can be canceled by the receipt of an appropriate time-out cancellation signal. 3. An event that occurs at the end of a predetermined period of time that began at the occurrence of another specified event. The time-out can be prevented by an appropriate signal.
Time Scale - 1. A time measuring system defined to relate the passage of temporal events since a selected epoch. Note: The internationally recognized time interval is the second. Time scales are graduated in intervals such as seconds, minutes, hours, days, and years, and in fractions of a second, such as milliseconds, nanoseconds, and picoseconds. 2. Time coordinates placed on the abscissa (x-axis) of Cartesian-coordinate graphs used for depicting waveforms and similar phenomena.
Time Scale Factor - A multiplier used to transform the real time of occurrence of an event or a problem into system time, such as that of a telecommunications system or a computer.
Time Server - The server maintaining and distributing the correct date and time over a computer network. Note: There is usually a special time-distribution protocol.
Time-Sharing - 1. The interleaving of two or more independent processes on one functional unit. 2. Pertaining to the interleaved use of computer time that enables two or more users to execute programs concurrently.
Time Slot - 1. Period of time during which certain activities are governed by specific regulations. [JP1] 2. A time interval that can be recognized and uniquely defined.
Time Stamp (TS) - 1. A data field in which is recorded (typically with a resolution of 1 millisecond) the cumulative variable queuing delay experienced by a packet in traversing the network. [After T1.509-1995] 2. With respect to a recorded network event, a data field in which is recorded the time (time of day or other instant of elapsed time) at which the event took place.
Time Standard - A stable device that emits signals at equal intervals such that their count may be used as a clock.
Time Tick - A time mark output of a clock system.
Time-Variant Value - In cryptography, a value that changes with each transaction or with each message value.
Timing Jitter - The short-term variations of the significant instants of a digital signal from their ideal positions in time. Here short term implies phase oscillations of frequency greater than or equal to 10 Hz. Timing jitter may lead to crosstalk and/or distortion of the original analog signal and is a potential source of slips at the input ports of digital switches. It may also cause slips and resultant errors in asynchronous digital multiplexes.
Timing Recovery - The derivation of a timing signal from a received signal.
Timing Signal - 1. The output of a clock. 2. A signal used to synchronize interconnected equipment.
Timing Tracking Accuracy - A measure of the ability of a timing synchronization system to minimize the clock difference between a master clock and any slaved clock.
T-Interface - For basic rate access in an Integrated Services Digital Network (ISDN) environment, a user-to-network interface reference point that (a) is characterized by a four-wire, 144-kb/s (2B+D) user rate, (b) accommodates the link access and transport layer function in the ISDN architecture, (c) is located at the user premises, (d) is distance sensitive to the servicing network terminating equipment, and (e) functions in a manner analogous to that of the Channel Service Units (CSUs) and the Data Service Units (DSUs).
Tip and Ring - An archaic term that gets its meaning from the old switchboard plugs. Each plug had a tip connector and a ring connector. Now, tip and ring refer to the two conductors that make up a single telephone line.
TLM - Abbreviation for telemetry.
TM - Abbreviation for transverse magnetic. See transverse magnetic mode.
TOD - Abbreviation for time of day. See time of occurrence.
Token - In certain local-area-network protocols, a group of bits that serves as a symbol of authority, is passed among data stations, and is used to indicate the station that is temporarily in control of the transmission medium.
Token-Bus Network - A bus network in which a token passing procedure is used.
Token Passing - A network access procedure in which a token passes from station to station and the only station allowed to transmit information is the station with the token.
Token Passing Bus LAN (IEEE 802.4) - A token passing bus LAN is a LAN using a deterministic access mechanism and topology in which all stations actively attached to the bus "listen" for a broadcast token or supervisory frame. Stations wishing to transmit must receive the token before doing so; however the next logical station to transmit may not be the next physical station on the bus. Access is controlled by pre-assigned priority algorithms.
Token Passing Ring LAN (IEEE 802.5) - A token passing ring LAN is a LAN using a deterministic access mechanism and topology, in which a supervisory frame (or token) is passed from station to adjacent station sequentially. Stations wishing to transmit must wait for the "free" token to arrive before transmitting data. In a token ring LAN the start and end points of the medium are physically connected, leading to a ring topology.
Token Ring Adapter - A network interface card (NIC) designed to attach a client workstation to a token ring computer network and operate as a token-passing interface.
Token-Ring Network - See network topology.
Toll Call - A call to any location outside the local service area. Otherwise known as a long distance call.
Tolerance - The permissible range of variation of some characteristic from its nominal value.
Tolerance Field - 1. The region between two curves, such as circles or rectangles, used to specify the tolerance on component size and geometry. 2. Pertaining to the cross section of an optical fiber, when used to specify the respective diameters and ovalities of, and concentricity error between, the core and cladding; two concentric annular regions which define the core-cladding boundary and the cladding outer boundary. Note: Dimensions are usually expressed in micrometers (
Toll Call - See long-distance call.
Toll Center - An office (or group of offices) within a city which generally handles the originating and incoming toll traffic for that city to or from other toll center areas and which handles through switched traffic. The toll center normally handles the inward toll traffic for its tributary exchanges and, in general, either handles the outward traffic originating at its tributaries or serves as the outlet to interexchange circuits for outward traffic ticketed and timed at its tributaries. Toll centers are listed as such in the Toll Rate and Route Guide.
Toll Center Area - The areas served by a toll center, including the toll center city and the communities served by tributaries of the toll center.
Toll Center Toll Office - A toll office (as contrasted to a local office) in a toll center city.
toll circuit - A general term applied to interexchange trunks used primarily for toll traffic.Toll Connecting Trunk - A general classification of trunks carrying toll traffic and ordinarily extending between a local office and a toll office, except trunks classified as tributary circuits. Examples of toll connecting trunks include toll switching trunks, recording trunks, and recording-completing trunks.
toll diversion - A system service feature by which users are denied the ability to place toll calls without the assistance of an attendant.Toll Office - A central office used primarily for supervising and switching toll traffic.
Toll Quality - The voice quality resulting from the use of a nominal 4-kHz telephone channel. Note: Toll quality may be quantized in terms of a specified bit error ratio.
Toll Switching Trunk - A trunk connecting one or more end offices to a toll center as the first stage of concentration for intertoll traffic. Note: Operator assistance or participation may be an optional function. In U.S. common carrier telephony service, a toll center designated "Class 4C" is an office where assistance in completing incoming calls is provided in addition to other traffic; a toll center designated "Class 4P" is an office where operators handle only outbound calls, or where switching is performed without operator assistance.
Tone - An electrically generated single-frequency sinusoidal oscillation.
Tone Detection Device - Tone detection devices "listen" for one of three things: 1.)CNG tones that automatically route the call to the fax if they are present, DTMF tones (DUAL TONE MULTIFREQUENCY) are commonly called "touch-tones" Modem calls are routed by DTMF placed in the dialing string from the connecting modem software. These extra digits are known as the security access codes (SAC)s. 3.) No tones - when there are no tones present, the device sends the call to the default device which is usually voice (phones, phone system, or answering machine). Tone detection devices require no additional services from the phone company to operate.
Tone Diversity - In a voice frequency telegraph (VFTG) transmission system, the use of two channels to carry the same information. Note: Tone diversity is usually achieved by twinning the channels of a 16-channel VFTG to obtain 8 channels with dual diversity.
Tone Signaling - See dual-tone multifrequency signaling.
Tool - Synonym utility program.
Top-Level Domain Name - In Internet addressing, a domain name identifying the highest hierarchical level in the geographical or organizational structure of the addressing system in Internet. Note: In Internet, the top-level domain name is either an ISO country name, or an English abbreviation such as "com," "edu," "gov," "mil," "net," or "org."
Topography - The specification and arrangement in physical locations of actual communication and information system components which implement the topology.
Topology - See network topology.
Torn-Tape Relay - An antiquated tape relay system in which the perforated tape is manually transferred by an operator to the appropriate outgoing transmitter.
Total Channel Noise - The sum of random noise, intermodulation noise, and crosstalk. Note: Total channel noise does not include impulse noise because different techniques are required for its measurement.
Total Harmonic Distortion (THD) - Of a signal, the ratio of (a) the sum of the powers of all harmonic frequencies above the fundamental frequency to (b) the power of the fundamental frequency. Note 1: The THD is usually expressed in dB. Note 2: Measurements for calculating the THD are made at the output of a device under specified conditions.
Total Internal Reflection - The reflection that occurs when light, in a higher refractive-index medium, strikes an interface, with a medium with a lower refractive index, at an angle of incidence (with respect to the normal) greater than the critical angle. See Snell's law
Total Line Length - In facsimile, the spot speed divided by the scanning line frequency. Note: The total line length may be greater than the length of the available line.
Touchpad - A pad that is electrically sensitive to touch, often used as the pointing device in laptops. You can also tap on it for clicks, but some people find that annoying if they bump the pad while typing.
Touch Panel - See touch-sensitive.
Touch Screen - See touch-sensitive.
Touch-Sensitive - Pertaining to a device that allows a user to interact with a computer system by touching an area on the surface of the device with a finger, pencil, or other object; for example, a touch-sensitive keypad or screen.
Touch Tone Dialing - See dual-tone multifrequency (DTMF) signaling.
Trace Packet - In a packet-switching network, a unique packet that causes a report of each stage of its progress to be sent to the network control center from each visited system element.
Trace Program - A computer program that performs a check on another computer program by exhibiting the sequence in which the instructions are executed and usually the results of executing the instructions.
Track - On a data medium, a path associated with a single read / write head position as data move past the head.
Trackball - A ball that can be rotated about its center and that is used as an input device, e.g., to position a cursor. Synonym control ball.
Track Density - The number of tracks per unit length, measured in a direction perpendicular to the direction in which the tracks are read.
Tracking Error - The deviation of a dependent variable with respect to a reference function.
Tracking Mode - An operational mode during which a system is operating within specified movement limits relative to a reference.
Tracking Phase - See tracking mode.
Traffic - 1. The information moved over a communication channel. 2. A quantitative measurement of the total messages and their length, expressed in CCS or other units, during a specified period of time.
Traffic Analysis - 1. In a communications system, the analysis of traffic rates, volumes, densities, capacities, and patterns specifically for system performance improvement. 2. [The] study of communications characteristics external to the text. 3. The analysis of the communications-electronic environment for use in the design, development, and operation of new communications systems. 4. In cryptology, the inference of information from observation and analysis of the presence, absence, amount, direction, and frequency of the traffic flow. 5. [The] Study of communications patterns.
Traffic Capacity - The maximum traffic per unit of time that a given telecommunications system, subsystem, or device can carry under specified conditions.
Traffic Encryption Key (TEK) - [A] key used to encrypt plain text or to superencrypt previously encrypted text and/or to decrypt cipher text.
Traffic Engineering - The determination of the numbers and kinds of circuits and quantities of related terminating and switching equipment required to meet anticipated traffic loads throughout a communications system.
Traffic-Flow Security - 1. The protection resulting from features, inherent in some crypto-equipment, that conceal the presence of valid messages on a communications circuit; normally achieved by causing the circuit to appear busy at all times. 2. Measures used to conceal the presence of valid messages in an on-line cryptosystem or secure communications system. Note: Encryption of sending and receiving addresses and causing the circuit to appear busy at all times by sending dummy traffic are two methods of traffic-flow security. A more common method is to send a continuous encrypted signal, whether or not traffic is being transmitted.
Traffic Intensity - A measure of the average occupancy of a facility during a specified period of time, normally a busy hour, measured in traffic units (erlangs) and defined as the ratio of the time during which a facility is occupied (continuously or cumulatively) to the time this facility is available for occupancy. Note: A traffic intensity of one traffic unit (one erlang) means continuous occupancy of a facility during the time period under consideration, regardless of whether or not information is transmitted. Synonym call intensity.
Traffic Load - The total traffic carried by a trunk or trunk group during a specified time interval.
Traffic Monitor - In a communications network, a service feature that provides basic data on the amount and type of traffic handled by the network.Traffic Over First Routes - A term applied to the routing of traffic and denoting routing via principal route for traffic between any two points as distinguished from alternate routes for such traffic.
Traffic Overflow - 1. That condition wherein the traffic offered to a portion of a communication system exceeds its capacity and the excess may be blocked or may be provided with alternate routing. 2. The excess traffic itself.
Traffic Padding - 1. In COMSEC, a countermeasure that generates spurious data in transmission media to make traffic analysis or decryption more difficult. 2. In reliability techniques, see pilot-make-busy circuit. 3. Generation of spurious communications or data units to disguise the amount of real data units being sent.
Traffic Register - See register.
Traffic Service Position System (TSPS) - A stored program electronic system associated with one or more toll switching systems which provides centralized traffic service position functions
