Mitigation method/Results/Conclusion A number of mitigation methods are available, though ideally it is better to solve the problem at source. It is imperative that the telecom operator is consulted when the electrification system is being planned and auto or booster transformers are suitably positioned to minimize induction effects due to the return currents. The balance of the pairs affected should be checked (> 60 dB), such that induction effects are minimized in the network cable. Measures that can be taken by the telecom operator to reduce the noise problem are to use screened cables, well earthed at the end of the parallelism as well as at numerous points along its length. If a screened cable is not available, then spare pairs, an old cable or a copper strip, earthed in a similar way can be almost as effective. Other measures may be to use induction-neutralising transformers (INTs) if a large number of customers are affected, or for fewer customers the use of common-mode chokes and drain circuits or even pair-gain systems. Occasionally, none of the above appears to work; this has been traced to the noise being conducted to the power system and local earth, such that all the customer internal wiring has an induced voltage on it. Fortunately, these are not too common. There is currently no easy solution to this case. References Rec. ITU-T K.37; Annexes A and B. Case study 1.9 – 2 –