Enterasys Networks XSR-3020 - Manual (Page 99)

Cable, CompactFlash and Accessory Specifications
XSR Getting Started Guide A-13
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 shown in Figure A-14 . The grounding shunt is also required to
insulate (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 or 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. The XSR requires that
you 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 2-1 to access the E1 card on the XSR.
RX In
TX Out
G.703 Balun Model 460 MC
NIM
-E1-CO
AX-BLN
J12 Transmit BNC
male connector
75-ohm connection
to your network
120-ohm
connection to XSR
J2 Receive BNC
male connector
75-ohm connection
to your network
Caution: The cable connecting the E1/ISDN PRI NIM to the balun requires 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.