[T]

T1 – (1) A 1.544 circuit with the equivalent of 24 analogs. (2) The basic 24-channel 1.544 Mbps pulse code modulation system used in the United States.

T-carrier – General designation of any digital transmission system.

Table driven – A logical computer process in which a user-entered variable is matched against an array of predefined values. Frequently used logical process in network routing, access security and modem operation.

Tail end hop off (TEHO) – Call in a private network which is carried over flat rate facilities (intermachine trunks or IMTs) to the switching node closest to its destination and is connected into the public network as a local call.

Tandem – A switching arrangement in which the trunk from the calling office is connected to a trunk at the called office through an intermediate point; serves to interconnect central offices when direct interoffice trunks are not available.

Tandem switching – The use of an intermediate switch or switches to interconnect circuits from the switch of one serving central office to the switch of a second serving central office in the same exchange.

Tandem switching system – See Tandem Tie Trunk Network.

Tandem tie trunk network (TTTN) – A serving arrangement which permits sequential connection of a group of private lines between PBX or CENTREX locations by utilizing a tandem switching operation.

Tandem trunking – Group of lines which connect two or more switches together.

tariff – The published rates, regulations and descriptions governing the provisions of communications service.

Task – A unit of work for the central processing unit.

Technical Operating Center (TOC) – Sprint location where telecommunications operations and equipment are tested and monitored; each center contains wire centers, test jacks, equipment racks, mux and radio equipment. [TOC operations include circuit installation, circuit maintenance and performance monitoring. Some, but not all TOCs, are equipped with switch equipment.]

Telco – Local telephone company; local exchange carrier.

Telecommunication lines – Circuits, trunks, cables and other links that are used to transmit messages from one location to another.

Telecommunications – The transmission of voice, video and/or data through a medium by means of electrical impulses; all aspects of information transmittal.

Telecommunications common carrier (TCC) – Person, firm or corporation that owns or operates telecommunications facilities for the purpose of providing either the facilities or services for profit.

Teleconference – Three or more people connected by telephone and capable of maintaining a continuous connection.

Telegraph – A device which interrupts or changes the polarity of DC current signaling to convey coded information.

Telegraphy – System of communicating coded information by the transmission of electrical signals generated by a telegraph key.

Telemetry – Transmission of a measurement over long distances, usually by electromagnetic means. Includes the apparatus for measuring, formulating and recording the value of a measured quantity at a distance. For example water level monitoring or flow-rate metering.

Telephone – Device which converts acoustical energy (sound) into electrical energy for transmission to a distant point.

Teletype – (1) Trademark of the Teletype Corporation.
(2) Frequently used as a generic name for keyboard/printers and for asynchronous transmission.

Teletypewriter – Machine used to transmit and/or receive communications on a printed page and/or tape.

Teletypewriter exchange service (TWX) – A service in which a customer’s leased teletypewriter is connected to a TWX switchboard to be routed over regular toll circuits to any other customer who subscribes to a similar service.

Terminal – (1) A point at which information can enter or leave a communications network. (2) A device for the input or output of data.

Terminal equipment - Devices, apparatuses and associated interfaces used to forward information to a local customer or distant point.

Termination – (1) Item such as a port that is connected to the end point of a circuit or equipment. (2) The points on a switching network to which a trunk or line may be attached.

Test marketing – Research conducted within a small targeted consumer group to determine the viability of an expanded program.

Test period – A defined amount of time used to measure circuit performance prior to releasing the circuit to a customer, usually after initial installation.

Tie-line - A private line communications channel provided by communications common carriers that links two or more points together.

Time division multiplexing (TDM) – (1) Sharing a single facility among several data paths by dividing up the channel capacity into time slices. (2) Equipment which enables the transmitting of signals over a single common path by transmitting them sequentially at different instants of time.

Time out – Set waiting period before a terminal system performs some action. [Typical uses include a poll release (when a terminal is disconnected if the time-out period elapses before keying resumes) or an access time-out.]

Time-sharing – The sharing of available processing time on a single computer system among multiple simultaneous users.

Token bus - Local network 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 physical station to transmit is not necessarily the next physical station on the bus. Bus access is controlled by preassigned priority algorithms.

Token passing – Local area network access technique in which participating stations circulate a special bit patter (the token) that grants network access to each station in sequence; often used in networks with a ring topology.

Token ring - Local network access and topology in which a supervisory frame or token is passed from station to station in sequential order. Stations wishing to gain access to the network must wait for the token to arrive before transmitting data. In a token ring, the next logical station receiving the token is also the next physical station on the ring.

Toll call – Any transmission on the public switched network to a point outside the local service area.

Toll center – Central office where operators (human or mechanical) are present to assist in completing incoming toll calls.

Toll office - Switching center where inter-city circuits terminate; usually one switching center in a city is designated as the toll office and is also used for mileage rate measurements.

Toll plant – Facilities that connect toll offices throughout the country.

Toll restriction – Arrangement by which some telephone lines are denied access to long distance circuits.

topology – Logical or physical arrangement of stations on a network in relation to one another. See bus, ring, star and tree.

Touch sensitive – System which identifies physical contact on a screen by coordinates and transmits the information to a computer to be translated into some system action.

Touchtone – (1) Refers to DTMF signaling equipment.
(2) Frequently used to describe telephone equipment with pushbuttons.

Touchtone adapter - Device that can be connected to a rotary dial telephone to allow for dual tone multifrequency tone (DTMF) signaling.

Trace – Technique used in trouble shooting and/or debugging computer programs and equipment.

Traffic – (1) All calls sent and received over a communications network. (2) The total information flow of a communications system at any given time.

Traffic measurement and recording systems (TMRS) – A computer-generated report with usage information of telephone systems; usually includes trunk utilization, outages, queuing time and the need for additional common equipment.

Traffic overflow – Condition that occurs when the number of calls to be processed exceeds the capacity of a particular trunk groups, and calls are redirected automatically or manually to another trunk group.

Traffic service position (TSP) - A computer-controlled operating position.

Traffic volume analysis – Study of call patterns in a communications network.

Transmission – The electrical transfer of a signal, message or other form of data from one location to another without unacceptable loss of information content due to attenuation, distortion or noise.

Transmission level – Level of signal power, normally 1,000 Hz, which should be measured at a particular reference point.

Transmission speed – Number of pulses or bits transmitted in a given period of time, usually expressed as bits per second (bps) or words per minute (wpm).

Transponder – Electronic device on-board a satellite to amplify signals prior to re-transmitting them back to earth.

Transport layer – In the OSI model, the network processing entity responsible for the end-to-end control of transmitted data and the optimized use of network resources; works in conjunction with the underlying network, data, link and physical layers.

Tree – Type of bus topology in which the network branches out at certain points along its length to connect stations or clusters of stations; also called a branching bus.

Truncation – (1) Removal of one or more digits, characters or bits from one end of a block of data when a string length or target variable has been exceeded. (2) To cut off at a specified spot.

Trunk - (1) Group of circuits that carry call traffic in and out of the switch. (2) Circuit or channel connecting two exchanges or two switching devices. (3) Circuit capable of being switched at both ends and provided with the necessary terminating and signaling equipment. [Trunk differs from a line which is a circuit, one end of which does not terminate on a switching machine.]

Trunk group – Arrangement of communications channels into an identical group.

Trunk side – Circuit termination that connects other central offices and the toll network.

Trunk type – Circuits that use the same type of equipment going to the same terminating location.

Trunk utilization report (TUR) – A computer printout detailing the traffic on a trunk.

Tuning – The process of adjusting system control variables to make the system divide its resources most efficiently for the workload.

Two-tier ratio – Rate structure with separate charges for on-net and off-net cities, that is cities served and not served directly by the Sprint network.

Two-way circuit - (1) A circuit in which information signals in both directions are carried by the same two-wire path. (2) A short-distance channel using a single send/receive pathway, usually two copper wires, connecting a telephone to a switch.