Chapter 3 - Troubleshooting; General; All Leds Are "Off; Alarm Led - TC Communications TC1720 User Manual

Rs-422/rs-449 async/sync fiber optic modem (with optional dual optics)

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Table Of Contents

Table of Contents

General

Typically, most problems encountered during installation are related to an improperly wired RS-442/449 cable

or a break in the integrity of the fiber optic link (cable or connectors).

All LEDs are "Off"

If no LEDs are lit on the unit, check the DC power supply, terminal block connector plug, and/or power

source. If the problem persists, contact the Technical Support Department at TC Communications, Inc.

Alarm LED

When there is an alarm condition, the red "ALARM" LED will be lit and the "RxA" LED will also flash to

indicate the optic signal has been lost. The Alarm will also trigger the dry contact relay switch.

Optic Cable Types

Conventionally, fiber optic cable with yellow-colored insulation is used for single mode applications; gray or

orange-colored insulated cable is for multimode use. If multimode cable is used in a single mode application,

the test results could be erroneous and confusing.

Calculating the Loss on the Fiber

The fiber optic link and/or the connectors are frequently the source of communication problems. If problems

are present, check the optic connectors and the integrity of the link first. Ideally, the link should be calibrated

for total loss after the installation has been completed. This will accomplish two things: (1) it will verify that

the total loss of the link is within the loss budget of the device and (2) it will provide a benchmark for future

testing. For example, a system that has been tested as having 6dB of signal loss when installed should not

suddenly test out as having a loss of 10dB. If this were the case, however, the fiber link or connector would

probably be the source of the problem.

These are the reference values we use to calculate the loss on the fiber:

Multimode 1310nm

Single Mode 1310nm

Single Mode 1550nm

*These numbers are listed for reference only. We recommend an OTDR reading be used to measure actual link loss.

RS-442/449 Cable Verification

1. Make sure the electrical signal connections match the pin assignments for the device (refer to page 3

for DCE/DTE pin connections). Verify signal connections by checking the status LEDs on the front panel

of the TC1720. Verify that the pin signal connections match the appropriate LED responses (see Figures

1, 2 & 3).

2. Be sure that all switches are set correctly. All the front panel DIP switches should be in up (off) position.

All the "SW1 Internal DIP Switches" are generally factory configured. However, the clock settings can

be user configured with SW1-5, SW1-6, SW1-7, and SW1-8, to suit the user's timing needs, refer to table

1 on page 5.

Important Warranty Note:

If the need arises for any internal configuration, please contact the Technical Support Department at TC

Communications, Inc @ (949) 852-1973. Warranty voided if product seal is broken.