CANOGA PERKINS 2240 Fiber Optic Modem - Manual (Page 85)

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Chapter 5
Troubleshooting
5.1 Diagnostic Procedures
The following procedures are intended for use in the event of a system failure, not during the
initial installation of a 2240 optical link. For initial installation checkout, see section 1.7. Also, see
Chapter 6, "Diagnostic Procedures", for detailed diagnostics.
5.2 Local and Remote Loopback
5.2.1 Loopback Tests
All 2240s have built-in Local and Remote Loopback. These tests can be used to verify the basic
operation of a 2240 system.
The test modes can be activated by setting the Loopback switch on the front panel or by turning
on the Local Loopback or Remote Loopback control leads in the electrical interface (supported
interfaces only). See Chapter 4, "Data Interfaces", for more information.
Whenever either modem has a Loopback selected, the Loop On indicators on both modems will
be on and the DSR signal on the interface may be negated (check strapping of interface). Figure
5-1 shows a local loopback configuration.
Figure 5-1 Local Loopback from User End of Fiber Link
NOTE: Interface control of the loopback tests is only supported on the following
modular interfaces: RS-423/RS-232C, RS-449/422, RS-530 and V.35.
HOST
TERMINAL HOST
TERMINAL USER
TERMINAL
TX
RX
RX
TX
LOOP
LED
ON
LOCAL
LOOP
LOOP
LOCAL
SYNC
SYNC
LOOP
OFF
LOOP
LED
ON
FIBER OPTIC LINK