T.120
The T.120, an ITU-T standard, is made up of a suite of communication and application protocols. T.120 protocols are designed for multipoint Data Conferencing and real time communication, including multilayer protocols which considerably enhance multimedia, MCU and codec control capabilities. Depending on the type of T.120 implementations, the resulting product can make connections, transmit and receive data and collaborate using compatible data conferencing features, such as program sharing, whiteboard conferencing and file transfer.

T.30
The T.30, an ITU-T standard, describes the overall procedure for establishing and managing communication between two fax machines.

T.38
The T.38, an ITU-T standard, defines procedures for real-time Group 3 facsimile communication over IP networks.

T1
T1 is a digital WAN carrier facility. T1 transmits DS-1-formatted data at 1.544 Mbps through the telephone-switching network, using AMI or B8ZS coding.

T1 Access Line
T1 Access line is a 1.544 Mbps T1 line that provides twenty-four 64 Kbps data channels and uses in-band signaling. This type of line can contain all switched channels, all nailed-up channels, or a combination of switched and nailed-up channels.

T1 Cable
T1 Cable refers to a physical cable for T1 Line. T1 cable is two twisted pairs of 22 AWG, 100 ohm wire with the added characteristic that each pair is individually shielded.

T1 Carrier
T1 Carrier is a dedicated phone connection, a time-division multiplexed digital transmission facility, supporting data rates of 1.544Mbits per second. A T-1 line actually consists of 24 individual channels, each of which supports 64Kbits per second. Each 64Kbit/second channel can be configured to carry voice or data traffic. Most telephone companies allow you to buy just some of these individual channels, known as fractional T-1 access. Developed in the 1960s, the T1 carrier is designed to operate full duplex over two pairs in unshielded twisted pair (UTP) cable.

T1 Line
T1 Line is a general term for a digital carrier typically leased from a local or long-distance provider, capable of transmitting 1.544 Mbps of electronic information. A T1 line is point-to-point, as opposed to a dialable ISDN line. T1 lines may be used fractionally or at their full bandwidth. E1 is the approximate European equivalent, prevalent also in Mexico. E.g., the UT video network is composed primarily of leased T1 lines that carry compressed video and Internet data between UT components.

T1 PRI Line
T1 PRI Line is a T1 line that uses 23 B channels for user data, and one 64 kbps D channel for ISDN D-channel signalling. The B channels can be all switched, all nailed up, or a combination of both. This type of PRI line is a standard in North America, Japan, and Korea.

T1/DS-1
T1/DS-1 is trunk level 1 that is the equivalent of 24 multiplexed voice grade channels at 64 Kbps. It is a dedicated phone connection with a total speed of 1,544 Mbps.

T2/DS-2
T2/DS-2, trunk level 2, is a facility that is equivalent of 4 multiplexed T1 Channels at a speed of 6.3 Mbps.

T3
T3 is a digital WAN carrier facility. T3 transmits DS-3-formatted data at 44.736 Mbps through the telephone switching network.

T3 Line
T3 Line is a high-speed connection capable of transmitting data at a rate of 45 Mbps. A T3 Line represents a bandwidth equal to about 672 regular voice-grade telephone lines. A T3 Line is typically installed as a major networking artery for corporations and universities with a high-volume network traffic.

T3/DS-3
T3/DS-3, trunk level 3, is a facility that is equivalent of 28 multiplexed T1 channels at a speed of 45 Mbps.

T4/DS-4
T4/DS-4, trunk level 4, is a facility that is equivalent of 6 multiplexed T3 channels at a speed of 274 Mbps.

TA: Terminal Adapter
Terminal Adapter (TA) is a device used to connect ISDN BRI connections to existing interfaces, such as EIA/TIA-232. Essentially, Terminal Adapter is an ISDN modem.

TAB: Telephone Answering Bureau
Telephone Answering Bureau (TAB), also called Telephone Answering Service, is a supplementary feature of telephone services whereby incoming calls on central office, Centrex Service, Inward Wide Area Telecommunications Service, Airport Telephone Service, and Administrative Terminal Lines may be answered at a common point through the use of answering lines and equipment. The service is available only where selective ringing is used. Various Telephone Answering Services are provided based on equipment, line configuration, and types of equipment used.

TABS: Telemetry Asynchronous Block Serial
Telemetry Asynchronous Block Serial (TABS) refers to the former AT&T polled point-to-point or multipoint communication protocol that supports moderate data transfer rates over intra-office wire pairs.

Tactical Designator
Tactical Designator, also called Tactical Callsign, refers a system consisting of a letter of the police phonetic alphabet followed by one or two numbers. For example, "Mary One" might identify the head of a city's homicide division.

TALI: Tekelec's Transport Adapter Layer Interface
Tekelec's Transport Adapter Layer Interface (TALI), a protocol in the SIGTRAN suite, is the interface of a Signaling Gateway, which provides interworking between the Switched Circuit Network (SCN) and an IP network. Since the Gateway is the central point of signaling information, not only does it provide transportation of signaling from one network to another, but can also provide additional functions such as protocol translation, security screening, routing information and seamless access to Intelligent Network (IN) services on both networks.

Talk Battery
Talk Batter refers to a DC voltage supplied by the central office to the subscriber's loop so as to supply the power to voice conversation.

Tandem Switching
Tandem Switching, also called class 4 switching, refers to the switching of long distance calls in PSTN. Tandem is a telephony term meaning "to connect in series." Thus, a tandem switch connects one trunk to another. A tandem switch is an intermediate switch or connection between an originating telephone call and the final destination of the call.

Tandem Tie Trunk Switching
Tandem Tie Trunk Switching is a switched network configuration in which transmission can be routed through two consecutive tie trunks.

Tandem Trunk
Tandem Trunk is a trunk circuit which connects a tandem switch to another tandem switch or to a telephone company central office.

TASI: Time Assignment Speech Interpolation
Time Assignment Speech Interpolation (TASI) is an analog technique used in telecommunications on certain long transmission links to increase voice-transmission capacity. Time Assignment Speech Interpolation works by switching additional users onto any channel temporarily idled because an original user has stopped speaking. While the original user resumes speaking, that user will, in turn, be switched to any cannel that happens to be idle.

TAT-12/13
TAT-12 is former AT&T's 12th and 13th transatlantic telephone cables in a ring structure which has been in operation since 1996, initially carrying 2x5 Gbit/s. This was the first TAT cable to use a ring structure, involving two stretches of cable across the ocean floor, which explains why two numbers (12 and 13) were used. All later cables also use a ring structure, but only use one number, TAT-14 etc.

TAT-8
TAT-8 is the 8th Transatlantic telephone transport cable. It initially carried 40,000 telephone circuits which means 40,000 simultaneous calls between USA, France, and UK. It was constructed in 1988 by a consortium of companies led by former AT&T, France Telecom, and British Telecom. It was able to serve the three countries with a single trans-Atlantic crossing with the use of an innovative branching unit located underwater on the continental shelf off the coast of Great Britain. The cable lands in Tuckerton, NJ, USA Widemouth, England, and Penmarch, France.

TBOS: Telemetry Byte Oriented Serial Protocol
Telemetry Byte Oriented Serial(TBOS) protocol is an open standard for network management, originally developed by Bellcore for AT&T. TBOS transmits alarm, status, and control points between NE and OSS. TBOS defines one physical interface for a direct connection between the telemetry equipment and the monitored equipment.

TCAP: Transaction Capabilities Application Part
Transaction Capabilities Application Part (TCAP), a protocol in the SS7 protocol suite, enables the deployment of advanced intelligent network services by supporting non-circuit-related information exchange between signaling points, using the Signaling Connection Control Part (SCCP) connectionless service. TCAP also supports remote control—ability to invoke features in another remote network switch.

T-Carrier
T-Carrier is a digital transmission system standardized by former AT&T for short and medium distance transmissions. T-Carrier is a PCM (Pulse Code Modulation) system using 64 Kbps for a voice channel.

T-CCS: Transparent Common Channel Signaling
Transparent Common Channel Signaling(T-CCS) is a feature that allows the connection of two PBXs with digital interfaces that use a proprietary or unsupported CCS protocol without the need for interpretation of CCS signalling for call processing. T1/E1 traffic is transported transparently through the data network and the feature preserves proprietary signalling. From the PBX standpoint, this is accomplished through a point-to-point connection. Calls from the PBXs are not routed, but follow a pre-configured route to the destination.

TCM: Trellis Coded Modulation
Trellis Coded Modulation (TCM) is one of the coded modulation techniques used in digital communications. It combines the choice of a modulation scheme with that of a convolutional code together for the purpose of gaining noise immunity over encoded transmission without expanding the signal bandwidth or increasing the transmitted power.

TDD: Telecommunications Device for the Deaf
Telecommunications Device for the Deaf (TDD) refers to a telephone service that is specially designed for people who have severe speech or hearing disabilities. As of January 26, 1992, all public entities were required by the ADA (Americans with Disabilities Act) to provide people who have severe speech or hearing disabilities equal access to emergency services. This means direct access to 9-1-1 using TTY/TDD's and computer modems. Telecommunicators must be able to effectively handle calls from the community with speech and hearing disadvantage. This involves dispatching these calls for assistance using the appropriate resources in a rational and timely manner. One of the most critical skills that a telecommunicator must possess is recognition of a TTY/TDD call. An entity may provide a separate seven-digit line for use exclusively by non-voice calls in addition to providing direct access for these calls on the 9-1-1 line. If 9-1-1 is not available, an entity can provide emergency service through a seven-digit number. It may provide two separate lines, one for voice calls and one for non-voice calls. If this is done, the entity must ensure that the services provided on the non-voice line are as effective in terms of time response and availability in hours as the voice line. Also this non-voice number must be publicized effectively as the voice number and displayed as prominently.

TDD: Time Division Duplexing
Time Division Duplexing (TDD) refers to a transmission scheme that allows an asymmetric flow for uplink and downlink transmission which is more suited to data transmission. In a Time Division Duplex system, a common carrier is shared between the uplink and downlink, the resource being switched in time. Users are allocated one or more timeslots for uplink and downlink transmission.

TDM Cross-Connect
TDM Cross-Connect allows DSO channels from one T1 or E1 facility to be cross-connected digitally to DS0 channels on another T1 or E1. By using this method, channel traffic is sent between a PBX and CO PSTN switch or other telephony device, so that some PBX channels are directed for a long-distance service through the PSTN while the router compresses others for interoffice VoIP calls. In addition, Drop and Insert can cross-connect a telephony switch (from the CO or PSTN) to a channel bank for external analog connectivity.

TDM: Time Division Multiplexing
Time Division Multiplexing (TDM) refers to a transmission technique in which a single communications channel is subdivided into a number of time slots, each of which carries the information of a separate data stream. Bandwidth is allocated to each channel regardless of whether the station has data to transmit.

Telco
Telco means a local or regional telephone company that owns and operates lines to customer locations and Class 5 Central Office Switches. Telcos have connections to other Cos (Central Office), Tandem (Class 4 Toll) offices and may connect directly to long distance carriers such as IECs.

Telco-Return CM
Telco-Return cable modem(CM) is a device which uses the cable network only for subscriber downstream traffic, and uses the PSTN for subscriber upstream traffic (which is necessary in older cable plants).

Telecommand
Telecommand refers to the transmission of non-voice signals for the purpose of remotely controlling a device.

Telecommunication
Telecommunication refers to the transmission of signals over a distance for the purpose of communication. Telecommunication is widespread and devices that assist the process such as the television, radio and telephone are common in many parts of the world. There is also a vast array of networks that connect these devices, including computer networks, public telephone networks, radio networks and television networks. Computer communication across the Internet, such as e-mail and instant messaging, is just one of many examples of telecommunication.

Telecommunication Circuit
Telecommunication circuit refers to a physical telephone and other communication path that is used to transmit information from one location to another. It is also called Telecommunication line.

Telecommunications Act of 1996
Telecommunications Act of 1996 refers to a United States telecommunications law, which was the first major overhaul of United States telecommunications law in nearly 62 years, amending the Communications Act of 1934. The general intention of the Act was deregulation and promotion of competition. The Act removed barriers which had previously prevented telecoms from competing head-to-head. A new group of telephone companies, "Competitive Local Exchange Carriers" (CLECs), grew to compete with the incumbents ("ILECs" or Incumbent Local Exchange Carriers). Deregulation and the new entrants provided consumers and businesses with choices in local phone service. When the smaller CLECs faced financial problems, the trend toward competition slowed, turning in to a decade of reconsolidation. The 1996 has widely been regarded by some as a failure. As former FCC Chair Reed Hundt stated, the telecommunications companies chose consolidation over competition. Ten years later, there are fewer telecommunications carriers then there were at the time of enactment. The US Congress is currently considering legislation that would essentially replace the Telecommunications Act of 1996.

Telecommunications Closet
Telecommunications Closet (TC), also called Wiring Closet, is a room or closet that houses all the telecommunication equipment. The TC also serves as a termination point for the horizontal cabling system of a network, the point of circuit administration and contains the network's distribution panels, cross-connects and backbone. The TC may also house auxiliary power supplies for workstation equipment.

Telecommunications Network
Telecommunications Network is a network of telecommunications paths arranged so that information may be passed from one part of the network to another over multiple paths. The following are some examples or Telecommunications Network: Computer network, the Internet, the public switched telephone network (PSTN). Telecommunications Network generally conceptually consists of three planes (so called because they can be thought of as being, and often are, separate overlay networks.): (1) The Control Plane is the part of the network that carries control information sometimes called signaling. (2) The Data Plane or User Plane is the part of the network that carries its user's traffic or messages. (3) The Management Plane is the part of the network that carries the operations and administration traffic required for network management.

Telecommunications Service
Telecommunications Service refers to the transmission, emission, or reception of intelligence of any nature, by wire, cable, satellite, fiber optics, laser, radio visual or other electronic, electric, electromagnetic, or acoustically coupled means , or any combination thereof.

Telecommunications Service Priority (TSP) System User
Telecommunications Service Priority (TSP) system user refers to any individual, organization, or activity that interacts with the NS/EP TSP System.

Telecommunications Tariffs
Telecommunications tariffs refer to the prices charged to consumers by telecommunications service providers.

Telecommuters
Telecommuters refers to those who are working remotely accessing the related resources by means of telecommunication. In today’s business climate, companies have become more distributed, and frequently work across time, space, and organizational boundaries. Telecommuters are increasing in the percentage of work force.

Teleconference
Teleconference refers to holding a conference via a telephone or network connection. The most simple form of teleconferencing is using three-way calling to setup your own teleconference. More advanced PBX equipment can setup conference calls between more than three participants. Computers have given new meaning to the term because they allow groups to do much more than just talk. Once a teleconference is established, the group can share applications and mark up a common whiteboard. There are many teleconferencing applications that work over private networks.

Teledesic
Teledesic is a global "Internet-in-the-Sky" that will provide broadband and Internet access, videoconferencing, high-quality voice and other digital data services through a constellation of 288 satellites. The Teledesic Network consists of terminals that interface between the satellite network and the terrestrial end-users, network gateways and network operations and control systems that perform network management functions, and a space segment that provides the communication links and switching among terminals. Teledesic's space-based network uses fast-packet switching to provide seamless, global coverage. Each satellite is a node in the fast-packet-switch network and communicates through crosslinks to other satellites in the same and adjacent orbital planes. Communications are treated within the network as streams of short, fixed-length packets. Each packet carries the network address of the destination terminal, and each node independently selects the least-delay route to that destination.

Teleflip
Teleflip is a service that makes it possible for a customer to send short email messages to anyone's phone using only their phone number. The way it works is like this: Open any email program or webmail site, then in the To: field, put your friend's phone number (don't use any parentheses around the area code), followed by @teleflip.com. For instance, if your friend's number was 415-555-1212, you'd just enter: 415-555-1212@teleflip.com. In the body of the message, type a short message, up to 160 characters. You can put something in the subject line too, but it will count towards that 160-character limit, finally,hit Send. Your message will go to TeleFlip, and TeleFlip will convert it into a text message and deliver it to your friend's phone via SMS (Short Message Service).

Telehealth
Telehealth is the use of electronic information and telecommunications technologies to support long-distance clinical health care, patient and professional health-related education, public health and health administration. Technologies used for this purpose typically are: videoconferencing, the Internet, store-and-forward imaging, streaming media, and terrestrial and wireless communications.

Teleoperation
Teleoperation refers to the operation of a machine at a distance. It is in analogy to the phrase "remote control". It's most commonly associated with robotics and mobile robots but can be applied to a whole range of circumstances in which a device or machine is operated by a person from a distance.

Telephone Number Mapping
Telephone Number Mapping, also referred to "E164 NUmber Mapping" or Electronic Numbering (ENUM), is a scheme for mapping telephone numbers to the Domain Name System (DNS) using Dynamic Delegation Discovery System(DDDS). ENUM includes a suite of protocols to unify the telephone numbering system E.164 with the Internet addressing system DNS by using an indirect lookup method, to obtain NAPTR records. The records are stored at a DNS database. ENUM is a DNS-based protocol that is best suited to offer services that not only help facilitate, but expand on ways to complete calls over VoIP networks. It provides a user with a domain name on an E.164 server in order to associate a common international telephone number with a URI and provide other DNS-related services. The server is maintained by the Service Provider and is expected to become a standard since it can successfully address locating URIs with nothing more than a common international telephone number.

Telephony
Telephony is a general term for the technologies behind voice communications, including traditional circuit switched telephone networks and the newer IP telephony technologies (VOIP) over the packet switched networks.

Teletext
Teletext is a one-way, or non-interactive, system for transmission of text and graphics via broadcasting or cable for display on a television set. A decoder or microchip resident in the TV set is needed to extract the teletext information. Teletext can be transmitted over one-way cable or over-the-air broadcasting via radio or television.

Telework
Telework, also called telecommuting, is the ability to do work at a location other than the "official duty station", using networking technologies. With portable computers, high speed telecommunications links, and ever-present pocket communications devices, many employees today can work almost anywhere.

Telex
Telex is a teletypewriter service allowing subscribers to send messages over the PSTN.

Terminal Equipment
Terminal Equipment (TE) refers to any ISDN-compatible device that can be attached to the network, such as a telephone, a fax, or a computer.

Terminated Line
Terminated Line is a transmission line with a resistance connected across the conductors at the far end. If this resistance matches the characteristic impedance of the line, no signals will be reflected from the far end to distort information transmissions.

Ternary Signal
Ternary Signal is a type of digital signal which has three voltage levels (e.g., +5v, 0v, and -5v).

Testing Signal
Testing Signal is a signal in telephony system used for measuring telephone circuit performance, such as noise bit error rate via loopback arrangement, and also to "trouble shoot" circuit problem and/or equipment faults.

TGW: Trunking Gateway
Trunking Gateway(TGW) is a gateway that supports only bearer traffic (no signaling traffic). For example, a gateway that terminates T1s (or greater) with no signaling control is a trunking gateway.

Third Party Billing
Third Party Billing refers to the use of an outside service bureau for bill processing such as: call rating, customer invoicing, collections, etc.

TIA/EIA-568 Standard
TIA/EIA-568 Standard refers to the complete electrical and physical guidelines for industry-standard premise wiring systems which were developed jointly by the Telecommunications Industries Association and the Electronic Industries Association. As specified by the TIA/EIA-568, a fully functional premise wiring system is the result of multiple subsystems working together as a single network.

TIA: Telecommunications Industry Alliance
Telecommunications Industry Alliance(TIA) is an organization that develops standards relating to telecommunications technologies. Together, the TIA and the EIA have formalized standards, such as EIA/TIA-232, for the electrical characteristics of data transmission.

TIA-232
TIA-232, a popular physical layer interface, also known as EIA-232 or RS-232, is a standard for serial binary data interconnection between a DTE (Data terminal equipment) and a DCE (Data communication equipment). It is commonly used in computer serial ports. A similar ITU-T standard is V.24.

TIA-422
TIA-422, also known as EIA-422 or RS-422, is the balanced electrical implementation of EIA/TIA-449 for high-speed data transmission. Now referred to collectively with TIA-423 as EIA-530, it provides for data transmission, using balanced or differential signaling, with unidirectional/non-reversible, terminated or non-terminated transmission lines, point to point, or multi-drop.

TIA-423
TIA-423, also known as EIA 423 or RS-423, is the unbalanced electrical implementation of EIA/TIA-449 for EIA/TIA-232 compatibility.

TIA-449
TIA-449, also known as EIA-449 or RS-449, specifies the functional and mechanical characteristics of the interface between data terminal equipment and data communications equipment. The electrical signalling standards intended for use with RS 449 are TIA-422 for balanced signals, and TIA-423 for unbalanced signals, with a data rate up to 2,000,000 bits per second. The standard specified two D-subminiature connectors with 37 and 9 pins for the primary and secondary data circuits.

TIA-530
TIA-530, also known as EIA-530 or RS-530, is a balanced serial interface standard that generally uses a 25-pin connector. The specification defines the cable between the DTE and DCE devices. It is a replacement for EIA-449, which uses 37-pin connector. It is to be used in conjunction with EIA-422 and EIA-423.

Tie Trunk
Tie Trunk is a special service circuit connecting two private branch exchanges (PBXs) or equivalent switching systems.

Tie-Line
Tie-Line specifies a connection that emulates a temporary tie-line trunk to a private branch exchange (PBX). A tie-line connection is set up automatically for each call and is torn down when the call ends.

Tie-Line Trunk
Tie-Line Trunk is a PBX trunk that is tied to a line, which leads to a remote PBX; typically used for private telephone networks, although the tie-line connection often is carried on telco-provided lines.

TIIAP: Telecommunications and Information Infrastructure Assistance Program
Telecommunications and Information Infrastructure Assistance Program (TIIAP) is a grant program from the National Telecommunications and Information Administration of the United States Department of Commerce, established by Congress in 1994 to assist non-profit organizations and units of state and local government to undertake projects which contribute to the building of a national information infrastructure.

Time Consistent Busy Hour
Time Consistent Busy Hour refers to the identical hour each day over a number of days, during which the highest average traffic is measured.

Time Division
Time Division refers to a method of serving a number of simultaneous channels over a common transmission path by assigning the transmission path sequentially to various channels, each assignment being for a discrete time interval.

Time Division Switching
Time Division Switching is switching of time-division multiplexed (TDM) channels by shifting bits between time slots in a TDM frame.

Time of Day Routing
Time of Day Routing is a routing scheme that routes calls to different locations based on the time of day when a call is made. For example, during business hours, calls can route to an office, and after hours, calls can go directly to a voice-messaging system or to a home number.

TINA: Telecommunications Information Networking Architecture
Telecommunications Information Networking Architecture(TINA) is a telecom services architecture defined by TINA-C. The resulting architecture specifications were consolidated as "TINA v1.0 Deliverables and Specifications" in September, 2000.

TINA-C: Telecommunications Information Networking Architecture Consortium
Telecommunications Information Networking Architecture Consortium(TINA-C) was an organization formed in 1993 by 46 of the world's leading Telco operators, vendors and IT industry with the mission to define a common software architecture for telecommunications. As a result, the "TINA architecture" was developed by a group of some one hundred engineers from its member companies, working together at one time under one roof in New Jersey, USA, as its core team. It was announced in September of 2000, that TINA-C had completed its mission and would be dissolved at the end of the year.

Tip
Tip refers to the ball-shaped contact at the end of a two-conductor switchboard plug in an old telephone system.

Tip and Ring
Tip and Ring are telephony slang for the two wires which make up the electrical circuit used for telephone wiring. Tip is the nickname for the electrically positive wire and Ring is the nickname for the electrically negative wire.

Tip Cable
Tip Cable is a small (usually 100-pair) cable connecting terminals on a distributing frame to cable pairs in the cable vault.

Tip Side
Tip Side is the conductor of a circuit which is associated with the tip of a plug, or of a telephone circuit. It is also called Tip Wire.

TIRKS: Trunk Information Record Keeping System
Trunk Information Record Keeping System(TIRKS) is a Bellcore OSS that provides records keeping for interoffice trunk facilities.

TL1: Transaction Language 1
Transaction Language 1 (TL1) is an element management protocol used primarily in the telecommunication industry. TL1 was designed by Bellcore (now Telecordia) in 1984 for use with its OSS (Operations Support System), MNA. TL1 is an MML (Man Machine Language), which means that TL1 messages should be readable and writeable by humans as well as machines.

TMN Model: Telecommunications Management Network Model
Telecommunications Management Network (TMN) model was introduced by ITU-T Recommendation M.3000 in 1985 as a reference model for the Operation Support System (OSS) of telecommunications service providers. The TMN concept is an architectural framework for the interconnection of different types of OSS components and network elements. TMN also describes the standardized interfaces and protocols used for the exchange of information between OSS components and network elements, and the total functionality needed for network management.

TMN: Telecommunications Management Network
Telecommunications Management Network(TMN) refers to the standard interfaces that would allow a network to be managed consistently across all network element suppliers. Telecommunications Management Network originated formally in 1988 under the auspices of the International Telecommunication Union (ITU-TS) as a strategic goal to create or identify such standard. The concept has fostered and tracked a series of interrelated efforts at developing standard ways to define and address network elements. Telecommunications Management Network uses the OSI Management Standards as its framework. Telecommunications Management Network applies to wireless communications and cable TV as well as to private and public wired networks.

Toll
Toll refers to, in telecommunications system: (1) the charge for making calls outside the boundaries of an exchange. (2) a general term applied to the facilities and services of carriers used in conjunction with making toll calls.

Toll Fraud
Toll Fraud refers to the fraudulent, illegal use of a company's telecommunications system by a third party from a remote location.

Toll Restriction PBX
Toll Restriction PBX refers to a PBX that permits a user to call within the local service area, but prevents toll calls to a toll operator without the assistance of an attendant. Toll restriction is available on an individual basis under either of the following options: (1) Battery Reversal: Provides a battery reversal signal from the central office on attempted toll calls which causes the PBX system to route the call to intercept tone. (2) 0/1: Screen calls from restricted lines, and routes calls in which the first or second digit following the access code is a 0 or a 1 to intercept tone. However, station users on 0/1 toll restriction lines can be allowed to make toll calls to up to ten preselected exchange or area codes.

Touch Tone
Touch tone refers to Dual Tone Multi Frequency (DTMF) that uses two tones to represent each key on the touch pad. When any key is pressed, the tone of the column and the tone of the row are generated, hence dual tone. As an example, pressing the '5' button generates the tones 770 Hz and 1336 Hz.

Traffic Capacity
Traffic Capacity refers to the total volume of traffic which a communications facility can handle within a specified time period.

Traffic Grooming
Traffic Grooming refers to the process of taking telecommunications traffic and sorting it into the most efficient arrangement possible. It involves the consideration of network topology and the different routes in use. When dealing with mesh networks, it's especially helpful.

Traffic Usage
Traffic Usage refers to the total occupancy of a network. This is calculated as the product of holding time and calling rate, and can be expressed as call-hours. Traffic usage may be made up of many short calls or a few long calls - it doesn't matter.

Traffic-Flow Security
Traffic-flow security refers to the use of measures that conceal the presence of valid messages on a communications circuit to prevent traffic analysts, normally achieved by causing the circuit to appear busy at all times. Traffic-flow security can be done by the protection resulting from features inherent in some crypto-equipment or by operational procedures.

Transmission
Transmission refers to the act of transmitting electrical signals (messages) and the associated phenonomena of radiant energy that passes through media. Signals can be a series of data unit, such as binary digits, or groups of those, variously called frames, blocks. Transmission has two aspects: (1) the dispatching by a sender, for reception elsewhere, of a signal, message, or any form of information. (2) the propagation of a signal by any means, such as by telegraph, telephone, radio, television, or facsimile via any medium, such as wire, coaxial cable, microwave, optical fiber, or radio frequency.

Transmission Block
Transmission block refers to the following meanings: (1) A group of bits or characters transmitted as a unit and usually containing an encoding procedure for error control purposes. (2) In data transmission, a group of records is sent, processed, or recorded as a unit. Transmission block is usually terminated by an end-of-block character (EOB), end-of-transmission-block character (ETB), or end-of-text character (EOT).

Transmission Coefficient
Transmission coefficient is the value of some quantity associated with the resultant field produced by incident and reflected waves at a given point in a transmission medium divided by the corresponding quantity in the incident wave. The ratio of the transmitted to incident energy flux or flux of some other quantity at a discontinuity in a transmission medium; for sound waves, it is called the sound transmission coefficient. The ratio of the transmitted flux of some quantity to the incident flux for a substance of unit thickness.

Transmission Impairments
Transmission Impairments is a condition that causes information to be lost in a signal. The following are some aspects of transmission impairments: (1) Attenuation. Signals loose power in time. (2) Dispersion. Signals tend to spread as they travel, with the amount of spreading dependent on the frequency. (3) Delay distortion. Due to velocity of propagation that varies with frequency. Thus, various frequency components of a signal arrive at the receiver at different times. (4) Noise; sources from Thermal, Intermodulation, Crosstalk.

Transmission Level
Transmission Level refers to the power of a transmission signal at a point on a transmission facility. It may be measured in absolute terms (dbm) or in a ratio to its level at some reference point (db).

Transmission Medium
Transmission medium refers to any material substance which can propagate waves or energy for telecommunications purposes. Transmission medium are classified as one of the following: (1) Guided (or bounded)- waves are guided along a solid medium such as a transmission line. (2) Wireless (or unguided) - Transmissions and receptions are achieved by means of an antenna.

Transmission Objectives
Transmission Objectives refers to the electrical performance characteristics for communication circuits, systems, and equipment based on both economic and technical considerations of telephone facilities, and on reasonable estimates of the performance desired. Characteristics for which objectives are stated include loss, noise, echo, crosstalk, frequency shift, attenuation distortion, envelope delay distortion, etc.

Transmission System
Transmission system consists of a set of hardware facilities and software that transits a signal from one place to another. The signal can be an electrical, optical or radio signal.

TRIP: Telephony Routing over IP
Telephony Routing over IP (TRIP) is a policy-driven inter-administrative domain protocol for advertising the reachability of telephony destinations between location servers and for advertising attributes of the routes to those destinations. TRIP's operation is independent of any signaling protocol; hence TRIP can serve as the telephony routing protocol for any signaling protocol.

Triple Order Tone
Triple Order Tone is one of the order tones that has three short spurts of high tone. This signal is three short spurts in quick succession and means that the operator should pass the office name only and wait for another order tone.

Trouble Tone
Trouble Tone, also called plugging up code tone, is a steady low tone. It is applied by an operator or test person at a B position in a manual office to the jack sleeve of a line or trunk in a calling multiple, to tell other operators that the line or trunk is in trouble.

TRS: Telecommunications Relay Service
Telecommunications Relay Service (TRS) is the service that provides a bridge for telephone calls between voice telephone users and people who are deaf, hard of hearing, or speech-disabled. TRS is mandated by the US gorvenment with Disabilities Act and is regulated by the Federal Communications Commission (FCC).

Trunk
Trunk refers to physical and logical connections between two switches across which network traffic travels. A switched backbone is composed of a number of trunks.

Trunk Member
Trunk Member refers to a single circuit or trunk in a trunk group.

Trunk Occupancy
Trunk occupancy refers to the percentage of time that trunks are in use. Trunk occupancy may also be expressed as the carried CCS per trunk.

TSAPI: Telephony Services Application Programming Interface
Telephony Services Application Programming Interface (TSAPI) is a call control model developed by Lucent and Novell for NetWare servers.

TSI: Time Slot Interchange
Time Slot Interchange (TSI) is the device in a switching system that permits any received incoming byte from an input tributary to be mapped to any outgoing or transmiting byte, respectively, on the associated output tributary.

TSI: Transmitting Subscriber Information
Transmitting Subscriber Information(TSI) is a frame that can be sent by the caller with the caller's telephone number that can be used to screen calls.

TSP: Telecommunications Service Priority System
Telecommunications Service Priority (TSP) system is a prioritizing service providing national security and emergency preparedness (NS/EP) that are vital to coordinating and responding to crises. As a result of hurricanes, floods, earthquakes, and other natural or man-made disasters, telecommunications service vendors may become overwhelmed with requests for new telecommunication services and requirements to restore existing telecommunications services. The TSP Program provides service vendors with a Federal Communications Commission (FCC) mandate for prioritizing service requests by identifying those services critical to NS/EP. A telecommunication service with a TSP assignment is assured of receiving full attention by the service vendor before a non-TSP service.

TSPS Busy Verification Tone
TSPS Busy Verification Tone is a variation of "Busy Verification Tone" which is 440 Hz at - 13 dBm0/frequency for an initial of 2 seconds on and then on again for 0.5 second every 10 seconds.

TSPS: Traffic Service Position System
Traffic Service Position System (TSPS) is former AT&T's 5ESS OSPS's ability to provide several applications simultaneously on one switching system. One switch with OSPS can serve up to 128 teams of operators handling different applications, such as directory, tool, and operator assistance.

TTY: Teletypewriter
Teletypewriter (TTY) is a communication terminal which is capable of receiving coded character signals from a communications network and converting these signals into printed pages. This specific term is a trademark of the Teletype Corporation, a former AT&T subsidiary.

TUA: TCAP-User Adaptation Layer
Teletypewriter (TTY) is a communication terminal which is capable of receiving coded character signals from a communications network and converting these signals into printed pages. This specific term is a trademark of the Teletype Corporation, a former AT&T subsidiary.

TUP: Telephone User Part
The Telephone User Part (TUP) provides the signaling backbone between switching elements for basic call establishment, supervision, and release of circuit switched network connections for telecommunications services. TUP supports analog and digital circuits, and limited call management signaling.

Two-Way Trunk
Two-Way Trunk is the trunk that can be seized at either end which means a traffic may be originated from both side of the trunk. Both sides of the trunk can be used as "outgoing trunk" as well as "incoming trunk".