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2270 Fiber Optic Modem
5.2.1 Local Loopback Test
When activated, the local loopback test will cause all data transmission from the near-end (local)
user device to be looped back toward the receive of that same device. No data is looped back to
the far-end (remote) user device unless a bidirectional Local Loopback method is selected (refer to
Table 5-A, Loopback Options ).
The loopback point is set at the electrical interface of the local modem (see Figures 5-2 and 5-3).
Refer to Chapter 3, Data Interfaces, for pin numbers.
Figure 5-2.
Bi-Directional
Local Loopback
Active
Figure 5-3.
Interface Only
Local Loopback
Active
Figure 5-4.
Optical Only
Remote Loopback
Active