电信专业英英词典T-3

（单词翻译:单击）

　　Transmission Facilities

　　Transmission facilities provide the communication paths that carry user and network control information between nodes in a network. In general, transmission facilities consist of a medium (e.g., free space, the atmosphere, copper² or fiber³ optic cable) and electronic equipment located at points along the medium. This equipment amplifies⁴ (analog systems) or regenerates⁵ (digital systems) signals, provides termination functions at points where transmission facilities connect to switching systems, and may provide the means to combine many separate sets of call information into a single "multiplexed" signal to enhance the transmission efficiency.

　　Transmission Impairments

　　Transmission impairments is the degradation⁶ caused by practical limitations of channels (e.g., signal level loss due to attenuation⁷, echo, various types of signal distortion, etc.), or interference induced from outside the channel (such as power-line hum or interference from heavy electrical machinery).

　　Transmission Medium

　　Transmission medium is any material substance or "free space" (i.e., a vacuum) that can be, or is, used for the propagation of suitable signals, usually in the form of electromagnetic (including light waves), or acoustic⁸ waves, from one point to another; unguided in the case of free space or gaseous⁹ media or guided by a boundary of material substance.

　　Transport Services

　　Transporrt Services are network switching, transmission and related services that support information transfer capabilities¹⁰ between originating and terminating access service facilities.

　　Trunk

　　In a network, a trunk is a communications path connecting two switching systems used to establish end-to-end connections between customers.

　　Twisted Pair

　　Twisted pair is the most common type of transmission medium, consisting of two insulated copper wires twisted together. The twists or lays are varied¹¹ in length to reduce the potential for interference between pairs. In cables greater than 25 pair, the twisted pairs are grouped and bound together in a common cable sheath. See unshielded twisted pair.

　　T-1 - A leased line connection that can carry 1,544,000 bits per second.

　　T-3 - A leased line connection that can carry 44,736,000 bits per second.

　　Tariff¹² - 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.

　　TCP/IP - See Transmission Control Protocol¹³/Internet Protocol

　　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. Mandated¹⁵ nationally by Congress with the passage of the Americans with Disabilities Act, it may also be called “Telecommunication¹⁴ Devices for the Deaf Tax.”

　　Telephone Network - The system of wires, fiber-optic cables, satellites and transmission towers that transmit telephone messages from caller to receiver.

　　Telnet - A program that allows Internet users to login to computers other than their host. Telnet also refers to the act of doing so.

　　Text Format¹ vs. HTML Format - Some Web applications, such as e-mail or Web pages, can either be viewed in Text or HTML formats¹⁶. Text formats generally display only the words (text) in an e-mail or on a Web page and not graphics¹⁷, such as artwork or photos. HTML format allows display of both text and graphics.

　　Toll¹⁸ Call - A call to any location outside the local service area. Otherwise known as a long distance call.

　　Transmission Control Protocol/Internet Protocol (TCP/IP) - A set of communications protocols¹⁹ or software necessary to access the Internet.

　　Trunk - A communication line between two switching systems. In other words, a telephone line.

　　TTY/TDD - Telephone Typewriter and Telephone Device for the Deaf. A telecommunication device for the hearing impaired²⁰ using teletypewriter principals. The users call a special operator number and third-party translation.