Specifications

92 AR Router
C613-03058-00 REV A
Figure57: Ethernet twisted pair (TP) loopback plug.
Figure58: Primary Rate ISDN 120Ω loopback plug.
Loopback Plugs for BRI Interfaces
If your router or expansion option’s BRI interface has an MC145474 or
MC145574 transceiver, a loopback plug is required before the BRI interface can
be tested. (Figure 60 on page 93 shows how to wire a suitable loopback plug.)
For all other transceiver types the test can be performed without a loopback
plug. In this case the Test Facility will still perform an internal loopback test,
but this will not test the complete physical interface. To fully test these
interfaces, an external NT mode device is required. Or, if the interface can be
configured for NT mode operation, an external TE device can be used.
To determine which type of transceiver a BRI interface uses, enter the
command:
SHOW BRI TEST
Figure 59 on page 93 shows an example of the output screen from the SHOW
BRI TEST command, with the transceiver type listed in the first line.
Not
connected
Not
connected
•Not
Twisted Pair (TP) Loopback Plug (RJ45 connector)
1
2
3
4
5
6
7
8
12345678
Switch or router
end view
TX+
TX-
RX+
RX-
TPLOOP
PRI Loopback Plug (RJ45 connector)
1
2
3
4
5
6
7
8
12345678
Switch or router
end view
TX+
TX-
RX+
RX-
P120LOOP