Page 2-61
Specifications
INTER-TEL
®
AXXESS
®
MANUAL VERSION 11.0 – May 2008
Basic Rate Interface Terminology
SPECIFICATIONS
2
Basic Rate Interface Terminology
4.214 The following terms are defined to clarify the functional aspects of the two different
types of BRI cards available for the system (see the diagram following the definitions):
• Terminal Equipment (TE): A general term for a device at the user end of a telephone
connection. BRS cards are connected to either a Network Terminator (NT) or a user
device. The BRS port is the TE when it is connected to a Network Terminator (NT). If a
user device is connected to the BRS port, then that device is the TE.
• Terminal Equipment Type 1 (TE1): An ISDN device that terminates the user end of a
telephone connection, such as an ISDN telephone, an ISDN modem, an ISDN LAN
bridge, or a video conference unit.
• Terminal Equipment Type 2 (TE2): A non-ISDN device that terminates the user end
of a telephone connection, such as an analog telephone, fax machine, or analog modem.
• Terminal Adaptor (TA): A device that terminates the ISDN connection and interfaces
to an analog user device, such as an analog telephone, fax machine, or modem.
• Network Terminator (NT): A general term for a device on the customer end of a con-
nection to the Central Office [Local Exchange in Europe] that resides between the
user’s terminating ISDN device (TE or TA) and the Central Office [local exchange].
For systems with BRS cards, the NT is the BRS port. In the U.S., the NT device is pro-
vided by the customer. In other countries this device is often supplied by the ISDN pro-
vider.
• Network Terminator 1 (NT1): The primary terminating device that resides between
the Central Office and the customer site. The Central Office [local exchange] side con-
nection to this device is called the U interface. The customer side connection is called
the T interface. A BRU port has a built-in NT1 on each port. With BRI (U.S. only), the
NT1 is normally provided by the local service company or consumer. With PRI, NT1 is
not normally provided by the local service company or consumer, instead the ISDN
provider or Central Office [local exchange] provides the NT1 for the customer location.
• Network Terminator 2 (NT2): This terminating device resides between the primary
terminating device (NT1) and the user’s ISDN device (TE or TA). The side of the con-
nection that links to the NT1 is called the T interface (see above), and the side that con-
nects to a user device is called the S interface. A BRS port is an NT2 device and so is
the T1/E1, T1C, and E1C.
BRI ISDN Reference Points
Central Office
ISDN
Provider
Terminal
TE 2
Adapter
U Interface
S Interface
T Interface
(Non-ISDN
Device)
S/T Interface
NT 1
(BRU)
NT 2
(BRS)
User Site
Device)
TE 1
(ISDN
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