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Mitigation measures for telecommunication installations
PART 2: CASE STUDIES
| Case study # |
1.10 |
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| Title |
RF welder interference
|
| Type of trouble |
Acoustic noise/Degradation.
|
| Source of trouble |
RF welders and coupling of the RF into the telephone with resultant demodulation at semiconductor junctions into "white" noise.
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| System affected |
Customer's equipment, office equipment.
|
| Location |
Customer premises.
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| Keywords |
High-frequency welder, common mode chokes, filtering.
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| Version date |
2004-01-01 |
| System configuration |
|
Normal PSTN circuit adjacent to a factory that uses an RF welder. Noise, sounding like loud "white noise", is only present during welding operations. Customer has normal telephones and wiring.
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| Measurement/Searching techniques/Experiment
|
|
Detection of the noise is by inference to the
location. It is unlikely to be due to a far-away electric
source. Coupling of the noise into the affected
telephones/wiring tends to be over a short distance, so it
does not normally affect many customers. |
| Mitigation method/Results/Conclusion |
|
There is not always an easy solution to the
problem. Internal wiring may need to be well screened to
minimize RF pickup and/or the use of ferrite rings on
telephone cords. |
| References |
Rec. ITU-T K.37; Annexes A and B. |
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