Basic Rate Interface (BRI) Card
The customer’s interface to the ISLU2. Three types of BRI cards
exist:
• U-Type for 2 wire
• T-Type for 4 wire.
The U and T type cards provide the customer with the 2B+D
capabilities. The Z card performs the analog to digital
conversion similar to the CODEC function in the Analog Line
Unit. These cards are mounted in groups of 32 and can be
mixed, or later, interchanged (with appropriate translation
updates). The only restriction is that the T card requires
four-wire cabling to the distributing frame.
BILLDATS
3
Billing and Data System.
Bit Contraction of Binary Digit. A single symbol, (1 or 0), that when
used in groups, represents the numbers, letters, and other
symbols of communications. Generally combined in groups of 5,
8, or 16.
BITS Building Integrated Timing Source.
Bits Per Second (bps)
Sometimes written as B/S or b/s. A measure of the speed with
which data communications can move over a line. The prefixes
K (for thousand) or M (for millions) are often used to represent
higher speeds.
Blocking A phenomenon in a communications network where one user
cannot reach another due to any one, or a combination of,
network resource limitations.
Buffer Part of a communications processor or switch used to store
information temporarily.
Byte A sequence of successive bits (most often a group of eight)
handled as a unit in computer manipulation or data
transmission.
Call A complete, 2-way interexchange of information between two or
more parties in a network. It will generally consist of a number
of sequential messages or transactions passed over
communications circuits in each direction.
Call Request A message from a network addressable entity to the network
requesting the establishment of a virtual call between that
network addressable entity and another network addressable
entity. In the specific case of an X.25 interface, a call request
packet is sent from a data terminal equipment to a data circuit
terminating equipment. This packet contains a logical channel
number, the calling and called data terminating equipment
addresses, and (optionally) a user facility indication and call
user data.
3. Registered trademark of AT&T Corp.
GLOSSARY 235-200-150
May 2003
Page G-2 Issue 3.00
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