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Mitigation measures for telecommunication installations
PART 2: CASE STUDIES
| Case study # |
1.7 |
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| Title |
Infrared movement-sensing lights |
| Type of trouble |
Degradation, abnormal operation, loss function. |
| Source of trouble |
Outdoors PIR lighting was creating noise on a number of telephone lines, sufficient to cause DSL circuits to fail. |
| System affected |
Customer's equipment/Access network. |
| Location |
Customer premises. |
| Keywords |
Emission, other (solved at source). |
| Version date |
2004-01-01 |
| System configuration |
A normal PSTN line, enabled for ADSL, suddenly started to
suffer from large numbers of transmission errors,
particularly in the early evening, when it got dark, and last
thing at night. A number of customers appeared to suffer from
the problem.
|
| Measurement/Searching techniques/Experiment |
A RF detector indicated that there was harmonic power
noise present, but no industry likely to cause the problem.
Using the RF detector to search the lead-in cables to each of
the premises found one to be particularly high in the
harmonic noise levels. Further investigation revealed that
the owner of the premises had used a 'spare pair' in his
telecoms cable as a power feed for his PIR (passive infra
red) outside lamp. The problem was compounded in that the
lamp controller also performed a dimming action. Once the
lamp was correctly wired, away from the telecoms cable, the
problem was solved. A similar lamp was procured for EMC
testing, as it was thought to possibly be too high on
emissions.
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| Mitigation method/Results/Conclusion |
Solved at source, rewired the lamp correctly.
|
| References |
Rec. ITU-T K.37; Annexes A and B. |
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