18
MODULAR FIBER CAMPUS DRIVER, MFCD PLUS
ER: Glows red to indicate the likelihood of a Bit Error in the received signal.
During the 511 or 511/E test, ER will flash to indicate that the Test Pattern
Detector has detected a bit error.
TM: Glows red to indicate that the ME620A or ME621A has been placed in Test
Mode. The unit can be placed in test mode by the local or remote user.
NS: Glows red to indicate that the local Campus Driver has not yet connected with
the remote Campus Driver.
5.3 Diagnostics
The Campus Drivers are equipped with V.54 diagnostics that may be used to to
evaluate the condition of the local and remote units, as well as the twisted-pair link
between them: local loopback (LAL) and remote digital loopback (DL).
5.3.1 L
OCAL
A
NALOG
L
OOPBACK
The Local Analog Loopback (LAL) test checks the operation of the local Campus
Driver and is performed separately on each unit. Any data sent to the local Campus
Driver in this test mode will be echoed back (returned) to the user device. (See
Figure 5-2
, below). For example, characters typed on the keyboard of a terminal
will appear on the terminal screen.
Figure 5-2. Local analog loopback.
To perform a Local Analog Loopback test, follow these steps.
1. Activate LAL either by moving the front panel toggle switch DOWN to
“Local,” or by raising the appropriate signal on the DTE interface. Once
Local Analog Loopback is activated, the Campus Driver transmit output is
connected to its own receiver. The test LED should glow.
