Introduction To Line Telecommunications

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17. Fault Finding And Troubleshooting


17. - Fault Finding And Troubleshooting


17.1 - Verification Of The Fault


17.2 - Guidelines To Resolving A Fault

17.3 - Reporting A Fault To The Manufacturer

17.4 - Little Green Men And Other Gremlins

17. - Fault Finding And Troubleshooting

Faultfinding and trouble shooting are an essential skill for the communications system engineer. As the systems become more complex the methods required to locate a fault also become more complex.

Whilst the basics of fault finding can be taught, the best training is experience and resolution of real faults on existing systems. Examples developed for training cannot fully incorporate all the dynamics found in a live system.

This section is intended only as a guide to fault finding and cannot be a comprehensive manual.

Before attending site check to see if that fault has been seen on other examples of the system and if so what the resolution was. There is no point re-discovering a known solution.

The maintenance engineer will require system manuals and a tool kit appropriate to the system being examined. As a minimum this should include a test telephone, multi-meter, line simulator or network tester and IDC insertion tool. Comprehensive screwdriver and pliers sets will also be useful. This is a smaller kit than the installer would have since there will not usually be a need to re-route or re-install large portions of the system.

In addition to the tools the engineer will require a selection of spare parts. These should be sufficient to enable
replacement of the major system components or be available for immediate delivery from their stores should they be required.

17.1 - Verification Of The Fault

The first step in the fault finding process is the verification and location of the fault. This will entail a visit to site to examine the fault first hand by a qualified engineer. Very often the description of the fault will provide a clue to the affected part of the system. In cases where there is no clear indication then the following sequence should lead to the fault being located and its cause identified.

17.1.1 - Operation

The first item for examination when tracing a fault, especially when working with a new system, is user operation. It is common for the users to expect the features to be accessible in the same way as their previous system.

Ask the users to demonstrate the fault and ensure that they are using the correct operational process for the system. Errors should be corrected and the customer informed of the mistake then trained in the correct procedure.

If the system operation is correct then the investigation must move on to the system itself.

17.1.2 - Installation

If operation can be eliminated as the cause then the installation is the next item to check. Begin by verifying the power supplies and fuses, replacing any found to be faulty or in poor condition.

Next examine the wiring and connections, ensure that they are correctly and securely connected. Move on to the IDF and MDF connections.

The site records will be useful when they include the installation records and notes.

17.1.3 - System Equipment - Hardware

If the fault cannot be traced to the operation or installation of the equipment then system hardware will require

Begin with the CCU and check for any warning tell-tales indicating a fault condition. Then work out from the CCU to all auxiliary equipment connected to the system.

The order of checking is not important provided all equipment is examined. It is usually easier to begin with the optional equipment as this is usually fitted locally to the CCU. Then check each of the incoming line ports or cards and the extensions themselves.

In a large or busy system it will be necessary to wait for a convenient time before the lines and extensions can be disconnected for testing and further disruption should be kept to a minimum during this procedure.

Hardware faults usually manifest themselves as an inconsistent response to certain actions or conditions. - Software

Assuming that the checks so far have revealed no problems check the system software and the software of the auxiliary equipment. Begin by ensuring that the most up to date versions are installed. If old software is in use the updated versions must be fitted as they may include a resolution to the problem and manufacturers do not resolve faults on obsolete software versions.

Next ensure that the system has been correctly programmed. The programming records will be vital for this.

Software faults will usually be identified as an unexpected, yet consistent, response to a certain set of actions or conditions.



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Extracted from

Introduction To Line Telecommunications
Copyright Panasonic Business Systems UK Ltd 2000