Specifications

Cable, CompactFlash and Accessory Specifications
A-74
Balun for E1 or PRI NIM Cards
Some overseas electrical systems require that you use a balun and grounding shunt when utilizing
an E1 or PRI NIM card on the XSR. A balun is an adapter employed to connect a 75-ohm coaxial
cable pair (2 BNC connectors) to a 120-ohm twisted pair cable (RJ-48C connector).
The balun and its connectors are illustrated in Figure A-14. The grounding shunt is also required
to ground unused pins of the RJ-48C connector.
To install the balun, attach the 75-ohm coaxial cables to the BNC connectors and a 120-ohm E1/
PRI cable to the RJ-48C port (see below for details}.
Figure A-14 Balun for E1 ISDN PRI Connection
Grounding Shunt for E1 NIM Cards
If you connect a balun to a 75-ohm line, you will also need to attach a grounding shunt (or
terminal strip) to any NIM pins whose RJ-48C connectors utilize the balun. You must use a shunt
(shown in Figure A-15), or terminal strip to ground pins 3 and 6 of the RJ-48C interface, which are
not needed to complete the connection.
Figure A-15 Sample Grounding Shunt
Refer to “Hardware Installation” on page 2-11 to access the E1 card on the XSR.
120-ohm connection
to XSR
J2 Receive BNC
female connector
J12 Transmit BNC
female connector
75-ohm connection
75-ohm connection to
to your network
your network
Caution: The cable connecting the E1/ISDN PRI NIM to the balun needs two more wires to
extend the chassis ground to the balun. Cables of this type are often provided by your supplier
who can customize them to your needs.