Legacy Glossary

This is a glossary of older terms. While many of the definitions are unchanged, some of the definitions may be out of date and some of the terms may no longer be in use in the Data Center industry. This legacy glossary provides definitions for hundreds of information and communications technology (ICT) and data center terms and acronyms. Arranged alphabetically and searchable, the glossary explains common industry vocabulary.
1 A B C D E F G H I K L M N O P R S T U V W Z

A networking protocol developed for the creation of a robust internet being a connection across a variety of local networking mechanisms. The protocol used to connect to and through what is known today as the internet. The internet uses a layered architecture with several protocols. The TCP (Transmission Control Protocol) defines session-based communications, and the IP (Internet Protocol) addresses the lower-level issues of packet fragmentation and routing


Time domain reflectometer




The degree or intensity of heat present in a substance or object

Temperature, Dew-point

The temperature at which water vapor has reached the saturation point (100% relative humidity)

Temperature, Dry-bulb

Temperature of air indicated by an ordinary thermometer

Temperature, Wet-bulb

The temperature indicated by a psychrometer when the bulb of one thermometer is covered with a water-saturated wick over which air is caused to flow at approximately 4.5 m/s (900 ft/min) to reach an equilibrium temperature of water evaporating into air, where the heat of vaporization is supplied by the sensible heat of the air


The entire test setup, including the SUT and any external systems used to drive, coordinate, or monitor the benchmark

Thermal Effectiveness

Measure of the amount of mixing between hot and cold airstreams before the supply air can enter the equipment and before the equipment discharge air can return to the air-handling unit

Thermal Efficiency

Energy output as a percentage of energy input of a machine or process

Thermal Storage Tank

Container used for the storage of thermal energy. Thermal storage systems are often used as a component of chilled-water systems


An arrangement of tubes for assisting circulation in a liquid through the use of capillary action


Telecommunications Industry Association

Tin Whiskers

See whiskers, tin


The unit of measure used in air conditioning to describe the heating or cooling capacity of a system. One ton of heat represents the amount of heat needed to melt one ton (2,000 lb) of ice in one hour. 12,000 Btu/h equals one ton of heat

Total Heat (Enthalpy)

See heat, total

Turn-down Ratio

Ratio representing highest and lowest effective system capacity. Calculated by dividing the maximum system output by the minimum output at which steady output can be maintained. For example, a 3:1 turn-down ratio indicates that minimum operating capacity is one-third of the maximum

Twisted Pair

A cable element that consists of two insulated conductors twisted together in a regular fashion to form a balanced transmission line (from ISO/IEC 11801: 1995)

Twisted-pair Cable

A bundle of multiple twisted pairs within a single protective sheath (from ISO/IEC 11801: 1995)