Loopback Plugs For Testing Interfaces - Allied Telesis AT-AR020 PRI E1/T1 Hardware Reference Manual

Hardware Reference
C613-03023-00 REV J

Loopback Plugs for Testing Interfaces

Loopback plugs are used in conjunction with the Test Facility software to test
the physical interfaces on all PICs except the AT-AR026 and AT-AR027 (see the
"Test Facility" on page 44
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
(hence loopback plug) and received at the same interface.
On interfaces with control signals, these are also looped back. The data
received on the interface is compared with the data transmitted on the interface
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.
Some interfaces (e.g., synchronous ports) require a specially built external
testing device (available from your Authorised Allied Telesyn distributor or
reseller) to be used in conjunction with the Test Facility.
The BRI interfaces do not require loopback plugs. The Test Facility will perform
an internal loopback test on these interfaces.
Table 20 lists the loopback plug wiring diagrams for each PIC interface type.
Table 20: Loopback plug pin wiring diagrams
Physical Interface
RJ-45 asynchronous interface
Ethernet AUI interface
Ethernet TP interface
Primary Rate interface
Basic Rate ISDN S/T (some)
Basic Rate ISDN S/T and U interfaces
Figure 28: RJ-45 loopback plug for testing asynchronous interfaces
RJ45 Asynchronous Port Loopback Plug (RJ45 connector)
(RING) 1
(DCD) 2
(DTR) 3
(GND) 4
(RXD) 5
(TXD) 6
(CTS) 7
(RTS) 8
of this Reference, and the Test Facility chapter of the
Loopback Method/Pin Wiring Diagram
Figure 28
Figure 29 on page 42
Figure 30 on page 42
Figure 31 on page 42
Figure 33 on page 43
No loopback plug required
8 7 6 5
End view
of plug
4 3 2 1
RJ45LOOP
41