| T: Abbreviation for tera. One trillion or 1012. |
| T1: In telecommunications, the cable used to transport DS1 service. |
| Tap Loss: In a fiber optic coupler, the ratio of power at the tap port to the power at the input port. |
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| Tap Port: In a coupler where the splitting ratio between output ports is not equal, the output port containing the lesser power. |
| T-Carrier: Generic designator for any of several digitally multiplexed telecommunications carrier systems. |
| TCP/IP: Abbreviation for transmission control protocol/Internet protocol. Two interrelated protocols that are part of the Internet protocol suite. TCP operates on the OSI transport layer and breaks data into packets. IP operates on the OSI network layer and routes packets. Originally developed by the U.S. Department of Defense. |
| TDM: See time-division multiplexing. |
| TDMA: See time-division multiple access. |
| TEC: Abbreviation for thermoelectric cooler. A device used to dissipate heat in electronic assemblies. |
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| Tee Coupler: A three-port optical coupler. |
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| 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. |
| Ternary: A semiconductor compound made of three elements (e.g., GaAlAs). |
| Thermal Noise: Noise resulting from thermally induced random fluctuation in current in the receiver’s load resistance. |
| Throughput Loss: In a fiber optic coupler, the ratio of power at the throughput port to the power at the input port. |
| Throughput Port: In a coupler where the splitting ratio between output ports is not equal, the output port containing the greater power. |
| TICL: Abbreviation for temperature induced cable loss. Optical loss as a result of extreme temperatures outside a fiber optic cable’s environmental specifications. |
| Tight-Buffer: A material tightly surrounding a fiber in a cable, holding it rigidly in place. |
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| Time-division Multiplexing (TDM): A transmission technique whereby several low-speed channels are multiplexed into a high-speed channel for transmission. Each low-speed channel is allocated a specific position based on time. |
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| Time-division Multiple Access (TDMA): A communications technique that uses a common channel (multipoint or broadcast) for communications among multiple users by allocating unique time slots to each user. Used extensively in satellite systems, local area networks, physical security systems, and combat-net radiosystems. |
| TMN: See telecommunications management network. |
| Token Ring: A ring-based network scheme in which a token is used to control access to a network. Used by IEEE 802.5 and FDDI. |
| Total Internal Reflection: The reflection that occurs when light strikes an interface at an angle of incidence (with respect to the normal) greater than the critical angle. |
| Transceiver: A device that performs, within one chassis, both telecommunication transmitting and receiving functions. |
| Transducer: A device that converts energy from one form to another, such as optical energy to electrical energy. |
| Transmitter: A device that includes a source and driving electronics. It functions as an electrical-to-optical converter. |
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| Transponder: The part of a satellite that receives and transmits a signal. |
| Tree: In communications networks, a physical topology consisting of a hierarchy of master-slave connections between a concentrator and other FDDI nodes (including subordinate concentrators). |
| Trunk: 1) In a communications network, a single transmission channel between two switching centers or nodes, or both. 2) A circuit between switchboards or other switching equipment, as distinguished from circuits which extend between central office switching equipment and information origination/termination equipment. Trunks may be used to interconnect switches, such as major, minor, public and private switches, to form networks. |
| TTL: Abbreviation fortransistor-transistor logic. An old logic family. |
| Twisted Pair (TP) Cable: A cable made up of one or more separately insulated twisted wire pairs, none of which is arranged with another to form quads. |
