Northern UTA220/UTA220k - Manual (Page 36)

4-2
UTA220/UTA220k
ISDN
Basic Rate Interface
Several types of ISDN network services are available. The
most common is Basic Rate Interface (BRI). BRI provides two
B-channels (bearer channels) and one D-channel (used to place
and release calls on the network).
B-channels, which operate at 64 kbps full-duplex, carry end-
to-end data between network terminals. B-channels can be
either circuit-switched (dial-up), allowing each call to be
placed to different endpoints, or permanently connected
(nailed) to a single endpoint. In some applications, B-channels
can also be used to carry packet-switched data, where each
frame of data can dynamically be sent to different network
users. The TA does not support packet-switching on a
B-channel.
The D-channel is primarily a control channel between the
network and the terminal device (such as a TA).
Terminal Adapters
Terminal adapters attach standard data terminals and voice
telephones to the ISDN, allowing them to send and receive
calls and data via the ISDN. Some terminal adapters (but not
the UTA220) support voice service, allowing a standard
(analog) telephone set to be connected to the ISDN.
The UTA220 operates on the ISDN BRI. It provides circuit-
switched data communications using circuit-switched
B-channels for data, and uses the D-channel for signaling only.
ISDN Basic Rate Interface Points
BRI points and the associated devices found on customer
premises are shown in Figure 4-1. The boxes in the diagram
represent devices, and the vertical lines represent defined
interface points. There are two types of DTEs represented in
the diagram:
• TE1 devices have a built in ISDN interface.
• TE2 devices do not have a built in ISDN interface, and
require a TA to interface with the ISDN.
The data terminal devices (DTEs) are located in the left of the
diagram. The TA is connected to the ISDN at the U interface.
An NT1 device is not required; the NT1 function is built into
the UTA220.