Hardware Reference
69
C613-03031-01 REV E
Basic Rate ISDN Interfaces
Basic Rate ISDN (BRI) interfaces support two 64K B channels and one D
channel. On some routers and expansion cards the operational mode of the BRI
ISDN interface (TE or NT) is determined by jumpers mounted on the CPU or
expansion card. Other models and expansion cards—in particular those with U
interfaces—only support TE mode.
See the description of the relevant router model in this Reference for details of
the locations and names of jumpers. See the
Integrated Services Digital Network
(ISDN)
chapter of your router’s Software Reference for a detailed description
of the two operational modes. The router should be configured as a TE for
normal operation.
The jumpers used to determine interface termination are normally removed as
the building wiring will provide the correct termination for an ISDN TE-to-NT
circuit. When the BRI is connected in a point-to-point configuration, the
jumpers may need to be installed to terminate the line pairs with internal 100
Ω
resistors.
See the description of the relevant router series (in this Reference) for details of
the locations and names of jumpers. The
Integrated Services Digital Network
(ISDN)
chapter of your router’s Software Reference also has additional
information. The BRI interface pin out is shown in Table 30 on page 69.
If you are unsure of whether to terminate the line or not, contact your ISDN service
provider or your authorised Allied Telesyn distributor or reseller.
Primary Rate ISDN Interfaces
Primary Rate ISDN interfaces on the AT-AR390 and AT-AR395 support
connection to either 75
Ω
or 120
Ω
networks. The 75
Ω
interfaces conform to the
standard BNC method of connection to 75
Ω
coaxial cable (Table 31 on page 70).
Since there is currently no official international standard for “pluggable”
connection to a 120
Ω
system, 120
Ω
interfaces employ the RJ-45 method of
connection used by most other manufacturers (Table 32 on page 70).
Primary Rate ISDN interfaces on the AT-AR020 PRI E1/T1 PIC and AT-AR025
PRI/G.703 PIC support connection to 120
Ω
networks using the RJ-45 method
of connection used by most other manufacturers (Table 32 on page 70). An
external balun is required to connect to a 75
Ω
network.
Table 30: Pinout of the Basic Rate ISDN interface.
Pin
S/T Interface Functions
U Interface Functions
1
-
-
2
-
-
3
TX+
-
4
RX+
positive (+)
5
RX-
negative (-)
6
TX-
-
7
-
-
8
-
-
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