Specifications

Hardware Reference 21
C613-03080-00 REV E
Loopback Plugs for Testing Switch Interfaces
Loopback plugs are used in conjunction with the Test Facility software to test
the physical interfaces on the switch (see the “Test Facility” section beginning
on page 22 of this Reference, and the Test Fa cil it y chapter of the AT-8600 Series
Software Reference). The purpose of a loopback plug is to connect the output
pins on the interface to the input pins so that any data transmitted over the
interface is looped back and received at the same interface.
Gigabit copper interfaces (as found on the AT-A39/T expansion module, and the
AT-8648T/2SP) cannot be looped back. Loopback plugs can only be used in conjunction
with 10/100 Ethernet interfaces.
On interfaces with control signals, these are also looped back. The data
received on the interface is compared with the data transmitted to determine
whether or not the interface is functioning correctly. In order to produce a
comprehensive test report for the interface being tested, most tests performed
by the Test Facility require a loopback plug to be inserted.
Figure 10: Ethernet twisted pair (TP) loopback plug
Not
connected
Not
connected
•Not
Twisted Pair (TP) Loopback Plug (RJ45 connector)
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Switch end view
of plug
TX+
TX-
RX+
RX-
RTPLOOPsw