Case study # 1.10 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. System affected Customer's equipment, office equipment. Location Customer premises. Keywords High-frequency welder, common mode chokes, filtering. 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. 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. Copyright © ITU 2010 – All Rights Reserved