T
T1
A digital transmission link with a capacity of 1.544 Mbit/s, used in North America. Typically channelized into 24 DS0s, each capable of carrying a single voice conversation or data stream. Uses two pairs of twisted pair wires.
T1 (T-carrier)
A digital transmission service leased from a telephone company. T1 is a 1.544 megabit channel that can handle 24 voice or data channels at 64 kilobits per second. T2 is a 6.312 megabit channel, and T3 is a 44.737 megabit channel. Because of it's high speed, many businesses lease T1 lines to link to the internet.
T1 Access Line
A 1.544 mbps T1 line that provides 24 56 kbps data channels and uses inband signaling. This type of line can contain all switched channels, all nailed-up channels, or a combination of switched and nailed-up channels. You can connect this type of line to standard voice or Switched-56 data services. Using a feature called Drop-and-Insert, the MAX can use a portion of a T1 access line for data purposes and pass the remaining portion of the line's bandwidth to a PBX for voice purposes.
T1 Channel
One of 24 channels on a T1 line.
T1 Line
A line that supports 24 64-Kbps channels, each of which can transmit and receive data or digitized voice. The line uses framing and signaling to achieve synchronous and reliable transmission. The most common configurations for T1 lines are ISDN Primary Rate Interface (T1 PRI) and unchannelized T1, including fractional T1.
T1 PRI line
A T1 line that uses 23 B channels for user data, and one 64 kbps D channel for ISDN D-channel signaling. The B channels can be all switched, all nailed up, or a combination of switched and nailed up. This type of PRI line is a standard in North America, Japan, and Korea. PRI stands for Primary Rate Interface. You can connect this type of line to standard voice, or Switched-56, Switched-64, Switched-384, Switched-1536, and MultiRate data services. Using a feature called PRI-to-TI conversion, the MAX can share the bandwidth of a T1 PRI line with a PBX.
T3
A digital transmission link with a capacity of 45 Mbps, or 28 T1 lines.
T3 Line
A digital transmission link consisting of 28 T1 lines with a total bandwidth of 44.736 Mbps.
TACACS
Terminal Access Concentrator Access Control Server. A very simple query/response protocol that enables the MAX to check a user's password, and enable or prevent access. A TACACS server supports only the basic password exchanges that PAP uses; it does not support CHAP.
TCP
Transmission Control Protocol
TCP/IP
Transmission Control Protocol/Internet Protocol. An open network standard that defines how devices from different manufacturers communicate with each other over interconnected networks. TCP/IP protocols are the foundation of the Internet.
TDM
Time Division Multiplexer (or Time Division Multiplexing) Terminal Adapter -- A device that allows analog voice and data devices to work through an ISDN connection. The terminal adapter is a protocol converter that adapts equipment not designed for ISDN, such as phones, faxes, and modems.
TE
Terminal Equipment
TEC
Thermal Electric Cooler. A device which uses the Peltier effect to heat or cool as necessary to keep the laser temperature constant.
TELENET
A public packet switched network using the CCITT X.25 protocols owned and operated by GTE.
TFTP
Trivial File Transfer Protocol. A simplified version of the File Transfer Protocol that transfers files but does not provide password protection or user directory capability.
TG
Transmitter Gain
TIA
Transimpedance amplifier
TVRO
Television, receive only. An earth station designed to handle downlink signals only.
Tagged Image File Format (TIFF)
A still graphics file format that handles monochrome, gray scale, and color images and uses a variety of compression methods. See JPEG and GIF.
Tariff
Documents filed by a regulated telephone company with a state public utility commission or the Federal Communications Commission. Document details services, equipment, and pricing publicly offered by the telephone company.
Telco
Telephone company.
Telecommunications Industries Association
The group responsible for setting telecommunications standards in the United States.
Telecommuter
A work-at-home computer user who connects to the corporate LAN backbone using remote access technologies (for example, using a modem over analog lines, ISDN Terminal Adapter (TA) or ISDN router over ISDN lines, or CSU/DSU over Switched 56 lines).
Telemedicine
A multimedia distance application in which an attending physician can consult with a remote specialist sharing test results such as X-rays and other data.
Telephony Application Programming Interface (TAPI)
From Microsoft and Intel, TAPI allows applications on client computers running Windows to access voice services on a server. TAPI lets PCs and telephone gear work together, including phone systems and PBXs. See TSAPI.
Telephony Services Application Programming Interface (TSAPI)
A telephony programming interface that links a PBX with a NetWare server so PCs and telephone gear can work together. See TAPI.
Telnet
Terminal-to-remote host protocol developed for ARPAnet. It is the TCP/IP protocol governing the exchange of character-oriented terminal data. This protocol is used to link two computers in order to provide a terminal connection to the remote machine.
Instead of dialing into the computer, you connect to it over the Internet using Telnet. When you issue a Telnet session, you connect to the Telnet host and log in. The connection enables you to work with the remote machine as though you were a terminal connected to it.
Terabit
One trillion bits.
Terminal
A computer that does not have its own processor and that must connect to a terminal server in asynchronous mode in order to use its CPU. VT100, ANSI, and TTY are all types of terminals.
Terminal Access Concentrator Access Control Server (TACAS)
A very simple query/response protocol that enables an access concentrator to check a user's password, and enable or prevent access. A TACACS server supports only the basic password exchanges that PAP uses; it does not support CHAP.
Terminal Access Controller (TAC)
A program and a piece of hardware that connects terminals to the Internet.
Terminal Adapter
A device that allows analog voice and data devices to work through an ISDN connection. The terminal adapter is a protocol converter that adapts equipment not designed for ISDN, such as phones, faxes, and modems.
Terminal Adapter (TA)
A TA is a protocol converter that adapts non-ISDN equipment (such as a phone, fax, or modem), and enables each device to work over an ISDN connection. A TA has two functions. First, it must change the format of transmitted data to match the V.120 standard for asynchronous transfer over a B channel. Second, it must provide a way of setting up and clearing calls, usually by means of Hayes AT commands. A TA is to an ISDN line what a modem is to an analog telephone line. However, some of the D-channel information does not pass through the TA, so non-ISDN equipment cannot take full advantage of ISDN facilities, such as Calling-Line ID (CLID).
Terminal Emulator
A program that makes your computer look like a terminal so that you can connect to a terminal server. Your computer acts like a terminal during the connection; all processing is taking place remotely. A terminal emulator is also called a terminal emulation program.
Terminal Server
A terminal server is a computing device to which a terminal can connect over a LAN or WAN link. A terminal communicates with the terminal server over an asynchronous serial port (typically an RS-232 port) through a modem. A terminal converts the data it receives from the terminal server into a display and does no further processing of the data. A terminal also converts the operator's keystrokes into data for transmission to the terminal server.
Terminal Server Session
An end-to-end connection between a terminal and a terminal server. Usually, the terminal server session begins when the call goes on line and ends when the call disconnects.
Thermal Electric Cooler
A device which uses the Peltier effect to heat or cool as necessary to keep the laser temperature constant.
Thick Ethernet
A term that describes a type of Ethernet cable. Thick Ethernet, or thicknet, is .4" diameter coaxial cable for Ethernet networks.
Thin Ethernet
A term that describes a type of Ethernet cable. Thin Ethernet, or thinnet, is .2" diameter coaxial cable for Ethernet networks.
Throughput
The actual speed of a network.
Time Division Multiple Access (TDMA)
Time Division Multiple Access: a multiplexing standard that divides each carrier into three time slots--with one subscriber per slot. Transmission signals are broken up into tiny packets of information--which are sent in timed bursts in the 30 megahertz range--and are reassembled at the receiving end.
Time To Live (TTL)
The hop limit counter (value=32) for IP packets.
Timeout
An event in which a device or user exceeded a configured time limit for responding to a device or process.
Token Ring
A network architecture that uses a ring topology, baseband signaling, and the token-passing media-access method. Token ring can operate at 1, 4, or 16 Mbps, and supports four-wire twisted pair or fiber-optic media.
Topology
The design of a network. Physical topology refers to the layout of the hardware. Logical topology refers to the paths that messages take to get from one node to another.
Traceroute
A superset of PING used to evaluate the hops taken from one end of a link to the other.
Traffic Contract
An asynchronous transfer mode (ATM) configuration that guarantees the delivery of a specified amount of data. While data above the traffic contract can still be delivered when network resources are available, data that exceeds the traffic contract can be delayed or lost when conditions are congested.
Traffic Shaping
In frame relay, a set of rules for defining traffic flow. The sender has a mechanism that ensures that the transmission of guaranteed packets occurs in a certain way. The network knows the kind of traffic to expect, and can monitor the behavior of the traffic. In asynchronous transfer mode (ATM), traffic shaping is a method of modifying the traffic characteristics of a stream of cells in order to achieve better network efficiency and meet all Quality of Service (QoS) objectives.
Transceiver
A device that connects a host interfaces to local area network. Ethernet transceivers contain analog electronics that apply signals to the cable and sense collisions.
Transduction
The basic concept behind voice transmission; the conversion of energy from one form into another.
Transimpedance amplifier
An electrical circuit or device that accepts a current at its input and generates a voltage at its output.
Transistor
A semiconductor device that amplifies a signal or opens and closes a circuit. In computers, it acts as a switch. Transistors and other devices -- such as resistors, capacitors and diodes -- make up logic gates. Logic gates make up circuits, and circuits make up electronic systems, such as computers. See for more info.
Transmission
Analog vs. digital transmission. Analog transmission requires more precision than a voice transmission; even if a slight error occurs during a conversation, the listener can usually compensate and understand the speaker.
Transmission Control Protocol/Internet Protocol (TCP/IP)
A protocol capable of linking different computer platforms across the Internet.
Transmitter
In fiber optic communications, a light source whose beam can be modulated and sent along an optical fiber, and the electronics that support it.
Trivial File Transfer Protocol (TFTP)
A simplified version of FTP that transfers files but does not provide password protection or user-directory capability. It is associated with the TCP/IP family of protocols. TFTP depends on the connectionless datagram deliver service, UDP.
Trunk
The communications circuit between two nodes.
Trunk Restoration
A process that reroutes the permanent virtual circuits (PVCs) on the backup trunk to the primary trunk.
Trunk Side
Trunk is a communication line between two switching systems. The term switching system typically includes equipment in a central office (telephone company) and PBXs. A tie trunk connects PBXs. Central office trunks connect a PBX to the switching system at the central office.
Trunk-side Connection
A line that extends from the telephone company’s central office (CO) to the telephone network. Typically, a trunk-side connection is high-bandwidth and all digital.
Tunneling
A way of overcoming protocol restrictions on a network by encapsulating packets that use one protocol inside packets that use a protocol supported by the network.
Twisted Pair
Relatively low-speed transmission medium consisting of two insulated wires - shielded or unshielded-in regular spiral patterns. The wires are twisted around each other to minimize interference from other twisted pairs in the cable. Twisted pair is common in telephone wiring and is increasingly common in data networks. Other high-speed forms of cable include coaxial and fiber optic cables.
Twisted-pair Cable
A cable consisting of four or more copper wires twisted together in pairs. Telephone wiring is an example of twisted-pair cable. Twisted-pair cable can be shielded or unshielded.
Two-wire Subscriber Loop
The two-wire WAN link connecting the customer premises equipment (CPE) to the carrier’s switch.
A digital transmission link with a capacity of 1.544 Mbit/s, used in North America. Typically channelized into 24 DS0s, each capable of carrying a single voice conversation or data stream. Uses two pairs of twisted pair wires.
T1 (T-carrier)
A digital transmission service leased from a telephone company. T1 is a 1.544 megabit channel that can handle 24 voice or data channels at 64 kilobits per second. T2 is a 6.312 megabit channel, and T3 is a 44.737 megabit channel. Because of it's high speed, many businesses lease T1 lines to link to the internet.
T1 Access Line
A 1.544 mbps T1 line that provides 24 56 kbps data channels and uses inband signaling. This type of line can contain all switched channels, all nailed-up channels, or a combination of switched and nailed-up channels. You can connect this type of line to standard voice or Switched-56 data services. Using a feature called Drop-and-Insert, the MAX can use a portion of a T1 access line for data purposes and pass the remaining portion of the line's bandwidth to a PBX for voice purposes.
T1 Channel
One of 24 channels on a T1 line.
T1 Line
A line that supports 24 64-Kbps channels, each of which can transmit and receive data or digitized voice. The line uses framing and signaling to achieve synchronous and reliable transmission. The most common configurations for T1 lines are ISDN Primary Rate Interface (T1 PRI) and unchannelized T1, including fractional T1.
T1 PRI line
A T1 line that uses 23 B channels for user data, and one 64 kbps D channel for ISDN D-channel signaling. The B channels can be all switched, all nailed up, or a combination of switched and nailed up. This type of PRI line is a standard in North America, Japan, and Korea. PRI stands for Primary Rate Interface. You can connect this type of line to standard voice, or Switched-56, Switched-64, Switched-384, Switched-1536, and MultiRate data services. Using a feature called PRI-to-TI conversion, the MAX can share the bandwidth of a T1 PRI line with a PBX.
T3
A digital transmission link with a capacity of 45 Mbps, or 28 T1 lines.
T3 Line
A digital transmission link consisting of 28 T1 lines with a total bandwidth of 44.736 Mbps.
TACACS
Terminal Access Concentrator Access Control Server. A very simple query/response protocol that enables the MAX to check a user's password, and enable or prevent access. A TACACS server supports only the basic password exchanges that PAP uses; it does not support CHAP.
TCP
Transmission Control Protocol
TCP/IP
Transmission Control Protocol/Internet Protocol. An open network standard that defines how devices from different manufacturers communicate with each other over interconnected networks. TCP/IP protocols are the foundation of the Internet.
TDM
Time Division Multiplexer (or Time Division Multiplexing) Terminal Adapter -- A device that allows analog voice and data devices to work through an ISDN connection. The terminal adapter is a protocol converter that adapts equipment not designed for ISDN, such as phones, faxes, and modems.
TE
Terminal Equipment
TEC
Thermal Electric Cooler. A device which uses the Peltier effect to heat or cool as necessary to keep the laser temperature constant.
TELENET
A public packet switched network using the CCITT X.25 protocols owned and operated by GTE.
TFTP
Trivial File Transfer Protocol. A simplified version of the File Transfer Protocol that transfers files but does not provide password protection or user directory capability.
TG
Transmitter Gain
TIA
Transimpedance amplifier
TVRO
Television, receive only. An earth station designed to handle downlink signals only.
Tagged Image File Format (TIFF)
A still graphics file format that handles monochrome, gray scale, and color images and uses a variety of compression methods. See JPEG and GIF.
Tariff
Documents filed by a regulated telephone company with a state public utility commission or the Federal Communications Commission. Document details services, equipment, and pricing publicly offered by the telephone company.
Telco
Telephone company.
Telecommunications Industries Association
The group responsible for setting telecommunications standards in the United States.
Telecommuter
A work-at-home computer user who connects to the corporate LAN backbone using remote access technologies (for example, using a modem over analog lines, ISDN Terminal Adapter (TA) or ISDN router over ISDN lines, or CSU/DSU over Switched 56 lines).
Telemedicine
A multimedia distance application in which an attending physician can consult with a remote specialist sharing test results such as X-rays and other data.
Telephony Application Programming Interface (TAPI)
From Microsoft and Intel, TAPI allows applications on client computers running Windows to access voice services on a server. TAPI lets PCs and telephone gear work together, including phone systems and PBXs. See TSAPI.
Telephony Services Application Programming Interface (TSAPI)
A telephony programming interface that links a PBX with a NetWare server so PCs and telephone gear can work together. See TAPI.
Telnet
Terminal-to-remote host protocol developed for ARPAnet. It is the TCP/IP protocol governing the exchange of character-oriented terminal data. This protocol is used to link two computers in order to provide a terminal connection to the remote machine.
Instead of dialing into the computer, you connect to it over the Internet using Telnet. When you issue a Telnet session, you connect to the Telnet host and log in. The connection enables you to work with the remote machine as though you were a terminal connected to it.
Terabit
One trillion bits.
Terminal
A computer that does not have its own processor and that must connect to a terminal server in asynchronous mode in order to use its CPU. VT100, ANSI, and TTY are all types of terminals.
Terminal Access Concentrator Access Control Server (TACAS)
A very simple query/response protocol that enables an access concentrator to check a user's password, and enable or prevent access. A TACACS server supports only the basic password exchanges that PAP uses; it does not support CHAP.
Terminal Access Controller (TAC)
A program and a piece of hardware that connects terminals to the Internet.
Terminal Adapter
A device that allows analog voice and data devices to work through an ISDN connection. The terminal adapter is a protocol converter that adapts equipment not designed for ISDN, such as phones, faxes, and modems.
Terminal Adapter (TA)
A TA is a protocol converter that adapts non-ISDN equipment (such as a phone, fax, or modem), and enables each device to work over an ISDN connection. A TA has two functions. First, it must change the format of transmitted data to match the V.120 standard for asynchronous transfer over a B channel. Second, it must provide a way of setting up and clearing calls, usually by means of Hayes AT commands. A TA is to an ISDN line what a modem is to an analog telephone line. However, some of the D-channel information does not pass through the TA, so non-ISDN equipment cannot take full advantage of ISDN facilities, such as Calling-Line ID (CLID).
Terminal Emulator
A program that makes your computer look like a terminal so that you can connect to a terminal server. Your computer acts like a terminal during the connection; all processing is taking place remotely. A terminal emulator is also called a terminal emulation program.
Terminal Server
A terminal server is a computing device to which a terminal can connect over a LAN or WAN link. A terminal communicates with the terminal server over an asynchronous serial port (typically an RS-232 port) through a modem. A terminal converts the data it receives from the terminal server into a display and does no further processing of the data. A terminal also converts the operator's keystrokes into data for transmission to the terminal server.
Terminal Server Session
An end-to-end connection between a terminal and a terminal server. Usually, the terminal server session begins when the call goes on line and ends when the call disconnects.
Thermal Electric Cooler
A device which uses the Peltier effect to heat or cool as necessary to keep the laser temperature constant.
Thick Ethernet
A term that describes a type of Ethernet cable. Thick Ethernet, or thicknet, is .4" diameter coaxial cable for Ethernet networks.
Thin Ethernet
A term that describes a type of Ethernet cable. Thin Ethernet, or thinnet, is .2" diameter coaxial cable for Ethernet networks.
Throughput
The actual speed of a network.
Time Division Multiple Access (TDMA)
Time Division Multiple Access: a multiplexing standard that divides each carrier into three time slots--with one subscriber per slot. Transmission signals are broken up into tiny packets of information--which are sent in timed bursts in the 30 megahertz range--and are reassembled at the receiving end.
Time To Live (TTL)
The hop limit counter (value=32) for IP packets.
Timeout
An event in which a device or user exceeded a configured time limit for responding to a device or process.
Token Ring
A network architecture that uses a ring topology, baseband signaling, and the token-passing media-access method. Token ring can operate at 1, 4, or 16 Mbps, and supports four-wire twisted pair or fiber-optic media.
Topology
The design of a network. Physical topology refers to the layout of the hardware. Logical topology refers to the paths that messages take to get from one node to another.
Traceroute
A superset of PING used to evaluate the hops taken from one end of a link to the other.
Traffic Contract
An asynchronous transfer mode (ATM) configuration that guarantees the delivery of a specified amount of data. While data above the traffic contract can still be delivered when network resources are available, data that exceeds the traffic contract can be delayed or lost when conditions are congested.
Traffic Shaping
In frame relay, a set of rules for defining traffic flow. The sender has a mechanism that ensures that the transmission of guaranteed packets occurs in a certain way. The network knows the kind of traffic to expect, and can monitor the behavior of the traffic. In asynchronous transfer mode (ATM), traffic shaping is a method of modifying the traffic characteristics of a stream of cells in order to achieve better network efficiency and meet all Quality of Service (QoS) objectives.
Transceiver
A device that connects a host interfaces to local area network. Ethernet transceivers contain analog electronics that apply signals to the cable and sense collisions.
Transduction
The basic concept behind voice transmission; the conversion of energy from one form into another.
Transimpedance amplifier
An electrical circuit or device that accepts a current at its input and generates a voltage at its output.
Transistor
A semiconductor device that amplifies a signal or opens and closes a circuit. In computers, it acts as a switch. Transistors and other devices -- such as resistors, capacitors and diodes -- make up logic gates. Logic gates make up circuits, and circuits make up electronic systems, such as computers. See for more info.
Transmission
Analog vs. digital transmission. Analog transmission requires more precision than a voice transmission; even if a slight error occurs during a conversation, the listener can usually compensate and understand the speaker.
Transmission Control Protocol/Internet Protocol (TCP/IP)
A protocol capable of linking different computer platforms across the Internet.
Transmitter
In fiber optic communications, a light source whose beam can be modulated and sent along an optical fiber, and the electronics that support it.
Trivial File Transfer Protocol (TFTP)
A simplified version of FTP that transfers files but does not provide password protection or user-directory capability. It is associated with the TCP/IP family of protocols. TFTP depends on the connectionless datagram deliver service, UDP.
Trunk
The communications circuit between two nodes.
Trunk Restoration
A process that reroutes the permanent virtual circuits (PVCs) on the backup trunk to the primary trunk.
Trunk Side
Trunk is a communication line between two switching systems. The term switching system typically includes equipment in a central office (telephone company) and PBXs. A tie trunk connects PBXs. Central office trunks connect a PBX to the switching system at the central office.
Trunk-side Connection
A line that extends from the telephone company’s central office (CO) to the telephone network. Typically, a trunk-side connection is high-bandwidth and all digital.
Tunneling
A way of overcoming protocol restrictions on a network by encapsulating packets that use one protocol inside packets that use a protocol supported by the network.
Twisted Pair
Relatively low-speed transmission medium consisting of two insulated wires - shielded or unshielded-in regular spiral patterns. The wires are twisted around each other to minimize interference from other twisted pairs in the cable. Twisted pair is common in telephone wiring and is increasingly common in data networks. Other high-speed forms of cable include coaxial and fiber optic cables.
Twisted-pair Cable
A cable consisting of four or more copper wires twisted together in pairs. Telephone wiring is an example of twisted-pair cable. Twisted-pair cable can be shielded or unshielded.
Two-wire Subscriber Loop
The two-wire WAN link connecting the customer premises equipment (CPE) to the carrier’s switch.
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