0-9  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-carrier system A hierarchy of digital transmission capabilities designed to operate at various rates, designated T1 (1.544 Mbps), T2 (6.312 Mbps), T3 (44.736 Mbps), and T4 (274.176 Mbps). T1/E1 lines A WAN backbone carrier facility (line) typically leased by a corporation or government from a telecom carrier to build a private WAN. T1 lines run at 1.544 Mbps and are typically found in the U.S. E1 lines are used overseas (mainly in Europe) and run at speeds of 2.048 Mbps. TL9000 A set of quality system requirements for telecommunications products and services created by a global group of service providers. TL9000 is the telecommunications industry's extension to the ISO 9000 quality system, whcih was developed by the Geneva-based International Organization for Standardization (ISO) in 1987. Telecommunications Act of 1996 A federal statute signed into law on February 8, 1996 "to promote competition and reduce regulation in order to secure lower prices and higher quality services for American telecommunications consumers and encourage rapid deployment of new telecommunications technologies." (Telecommunications Act of 1996.) The legislation required regional Bells to implement Local Number Portability by the end of 1998. It also allowed regional Bells to offer long-distance service if they met certain competitive requirements for their home markets. terabit One trillion bits. terabits per second (Tbps) (1 trillion bits per second)-an information-carrying capacity measure used for high-speed optical data systems. terrestrial On land (versus submarine). thin film 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 wave guides, and may be used in integrated optical circuits thin film transfer (TFT) A display technology used for active matrix LCD screens that assigns a tiny transistor to each pixel, thus allowing the pixels to be controlled independently from one another. TFT screens are much quicker then traditional LCD screens, and have higher contrast ratios and wider viewing areas. third-generation (3G) The next generation of wireless technology beyond personal communications services. The World Administration Radio Conference assigned 230 MHz of spectrum at 2 GHz for multimedia 3G networks. These networks must be able to transmit data at 144 Kbps at mobile user speeds, 384 Kbps at pedestrian user speeds, and 2 Mbps in fixed locations. The International Telecommunication Union seeks to coordinate 3G standards through its International Mobile Telecommunications-2000 (IMT-2000) project, which sometimes serves as an alias for 3G. Current proposed standards for 3G networks include W-CDMA (Wideband CDMA) and cmda2000. time division multiple access (TDMA) A digital encoding scheme used in cellular service, this transmission method allows users to simultaneously transmit on the same frequency by allocating each user a discrete time slot. time division multiplexing (TDM) An electrical digital multiplexing technique that allows multiple streams of information to share the same transmission media. For transmission at 155 Mbps or above, the electrical spanM signal is typically converted to an optical signal for transport. SONET and SDH standards in North America and the rest of the world, respectively, set the bit rates, frame formats, and other physical and operational characteristics for these optical signals. total access communication system (TACS) An analog cellular phone system that was modeled after the U.S. analog advanced mobile phone services (AMPS) system, and deployed mostly in Europe. traffic analyzer In a communications system, the analysis of traffic rates, volumes, densities, capacities, and patterns specifically for system performance improvement. transceiver A device that performs, within one chassis, both transmitting and receiving functions. transmission control protocol/internet protocol (TCP/IP) A networking protocol used on the Internet that links dissimilar computers across interconnected networks, and creates links between computers with different device hardware, architectures, and operating systems. TCP ensures that a message is sent accurately and in its entirety. TCP breaks individual messages into data packets so that no two computers will monopolize the network. TCP then marks each of these packages with sequence numbers to ensure that they are reassembled in the right order by the receiving computer or browser. IP is the messenger protocol of TCP/IP that essentially addresses and sends packets. IP implements the network layer of the protocol, which contains a network address and is used to route a message to a different network or sub-network. The IP protocol relies on three pieces of information to receive and deliver information: IP address, subnet mask, and default gateway. transmission laser The laser that supplies the light to send a signal down an optical network. transmission speed In facsimile, the interval between the start of picture signals and the detection of the end-of-message signal by the receiver for a single document. transmitter Optical transmitters consist of an optical source (laser or LED), an information source, a modulator, and a power amplifier. transparent optical networks The original vision of the all-optical network as a network in which a signal is transported from source to destination in the optical domain. After entering the network, the signal is not converted to the electrical domain until it reaches its destination. Signals are amplified, shap. Thdemultiplexed, re multiplexed, and switched in the optical domain with no regard of the digital content of the signal, e.g., bit rate, modulation scheme, or protocol. Transparent optical networks are limited by (1) analog signal defects, such as gain tilt, ASE noise, chromatic dispersion, and crosstalk, that accumulate over distance; and (2) the difficulty of monitoring performance and isolating faults as a signal traverses a network. transponder A transponder is a signal receiver that automatically responds to a received signal. Some transponders forward a signal along a designated path at the same frequency or another frequency. Some transponders automatically return a programmed message. Transponders are often used as input interfaces for WDM systems. trunking network A telephone network that connects two telephone switches or two telco local offices. trunks integrated records keeping system (TIRKS) An operations support system developed by the Bell System to mechanize circuit-provisioning function. TIRKS maintains inventory information on all assignable components for trunks and special-service circuits. tunable laser A laser with an output frequency that can be varied during use. twisted-pair wire A wire made of two separately insulated strands of wire twisted together.