Chapter 7: Service and troubleshooting
EST3X Technical Reference Manual 181
Table 48: 3-MODCOM LINE 1 and LINE 2 LED states
state LINE 1 description LINE 2 description
There is no activity There is no activity
LINE 1 has been seized LINE 2 has been seized
Dialer or modem data is being
passed on LINE 1
Dialer data is being passed on
LINE 2 (modem data is passed only
on LINE 1)
LEDs) The application code or configuration code is downloading from the
CPU or 3-SDU
There is ringing on LINE 1
(flashing pattern detected)
N/A (LINE 2 does not have ring
detection)
Audible diagnostics
Obtain an audio amplifier device locally for listening to the distinctive sounds
associated with dialing, receiving handshakes, transmitting data, and receiving
acknowledgements. Place a 0.1 μF, 200 V or greater capacitor in series with one
of the leads. Alternately, you can use a lineman’s handset in monitor mode.
During downloading from a remote computer, you will hear the distinct sound of
modems establishing a connection, and then a series of rapid chirps as data is
transmitted.
Note: Remove the audio amplifier when you finish troubleshooting.
Common problems
Evaluation of visual and audible indications will usually serve to isolate the
source of trouble. Before replacing a 3-MODCOM, investigate the following
common causes of a module problem.
• The module is not properly seated on the electronics chassis, or one or more
connector pins are bent away from the associated connectors
• A modular telephone plug is not connected to the appropriate line 1 or
line 2 jack, is not fully seated, or is not connected at the telephone block
• The module is configured with incorrect CMS telephone numbers
• The telephone line is faulty
If the module and telephone line are okay, check the CMS telephone number by
dialing it using a standard telephone plugged directly into the RJ-31X jack. (The
jack will accommodate a standard modular phone plug.) You should:
1. Hear a dial tone when going off-hook
2. Lose the dial tone after dialing the first digit
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