T1
An AT&T term for a digital carrier facility used to transmit a DS-1 formatted digital signal at 1.544 megabits per second.

T3
A term for a digital carrier facility used to transmit

Tags
Formatting codes used in HTML documents. These tags indicate how the parts of a document will appear when displayed by a Web client program.

Taskbar
An area that runs across the bottom (usually) of the Windows 95 desktop. Running applications are represented as buttons on the taskbar, the current window is shown as a depressed button, all other applications are displayed as raised buttons.

TCP
Transmission Control Protocol. This is a transport layer protocol that establishes a reliable, full duplex, data delivery service used by many TCP/IP application programs. The TCP software uses the IP protocol to transmit information across the Internet.

TCP/IP
Transmission Control Protocol/Internet Protocol. A set of protocols, resulting from ARPA efforts, used by the Internet to support services such as remote login (TELNET), file transfer (FTP) and mail (SMTP).

TELNET
The Internet standard protocol for remote login (terminal connection) service. TELNET allows a user at one site to interact with a remote timesharing system at another site as if the user's terminal were connected directly to the remote computer.

Terminal
Communication device that lets a user send information to a computer by typing on a keyboard, and prints responses from the computer on paper or a screen.

Terminal Mode
Many communications programs allow you to mimic a computer terminal, which is basically a keyboard and CRT display and/or a printer. A common terminal mode emulator is VT-100.

Terminal Ready (TR)
This light is illuminated when your computer has turned on the RS-232 (serial) interface. Sometimes this light will not come on until you have loaded your communications software into memory.

Terminal Server
A small, specialized, networked computer that connects many terminals to a LAN through one network connection. A terminal server can also connect network users to asynchronous ports or a host.

Thermal Wax Transfer
A printing process using small heating elements to melt dots of wax pigment on a carrier film, which are then transferred to paper or transparent film by contact. This differs from the dye sublimation process in that individual dots do not fuse together, so thermal wax transfer appears to be of a lower resolution.

Thread
In the context of Windows NT, a thread is sometimes used to refer to an NT service. Threading also refers to a low-level system architecture concept used in some multitasking operating systems.

Threshold
The point at which an action begins or changes. The threshold setting used in scanning line art determines which pixels are converted to black and which will become white. The threshold defined in the USM process determines how large a tonal contrast must be before sharpening will be applied to it.

TIFF
Tag Image File Format. A graphic file format, TIFF files are also bit maps, but they can be any size, resolution, or color depth. It is the most versatile, reliable, and widely supported bit-mapped format and is the standard format for saving scanned images. However, the format does have several variations which means that occasionally an application may have trouble opening a TIFF file created by another program.

Title bar
The horizontal bar at the top of a window. The title bar shows the name of the window.

Tone Curves
Also known as gamma curves. These are used to smoothly adjust the overall tonal range of an image, or the individual tonal ranges of each color channel.

Toolbar
A collection of buttons that typically make the more common tools for an application easily accessible.

TSR
Terminate and Stay Resident.