Glossary:

ATIS Telecom Glossary

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Select a term name to open its entry and any media references. Longer definitions end with a “Read More” link.

unit interval

In isochronous transmission, the longest interval of which the theoretical durations of the significant intervals of a signal are all whole multiples.

unit-distance code

An unweighted code that changes at only one digit position when going from one number to the next in a consecutive sequence of numbers.
Note 1: Use of one of the many unit-distance codes can minimize errors at symbol transition points when converting analog quantities into digital quantities.
Note 2: An example of a unit-distance code is the Gray code.… (Read More →)

Universal Personal Telecommunications (UPT) service

A telecommunications service that provides personal mobility and service profile management.
Note 1: UPT service involves the network capability of identifying uniquely a UPT user by means of a UPT number.
Note 2: The general principles of UPT are given in ITU-T Recommendation F.85
0.
Note 3: UPT and PCS are sometimes mistakenly assumed to be the same service concept.… (Read More →)

universal service

The concept of making basic local telephone service (and, in some cases, certain other telecommunications and information services) available at an affordable price to all people within a country or specified jurisdictional area.

Universal Time (UT)

1. The basis for coordinated dissemination of time signals, counted from 0000 at midnight.
2. In celestial navigation applications, the time which gives the exact rotational orientation of the Earth obtained from UTC by applying increments determined by the U. S. Naval Observatory.
3. A measure of time that conforms, within a close approximation, to the mean diurnal rotation of… (Read More →)

UNIX

TM: A portable, multiuser, time-shared operating system that supports process scheduling, job control, and a programmable user interface.
Note 1: There are many proprietary operating systems that are based on UNIXTM and are commonly referred to as UNIXTM, but are not necessarily interoperable.
Note 2: Most UNIXTM-based operating systems are POSIX compliant.

unnumbered command

In a data transmission, a command that does not contain sequence numbers in the control field.

unnumbered information (UI) frame

A frame used to transfer unacknowledged information between two link layer entities. The format and encoding are the same as specified in Recommendation
0. 921/
1.
44
1. The CRC (cyclic redundancy check) is derived over the entire frame. [T1.509-1995]

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