HI FRIENDS i am working as telecom technician.in my section under groundtelephone cables are affected by railway electric traction inductance. telecom signal voltage is 48-52 v dc .jan 15 started electric railway traction after that problem started .train moving time telecom cable voltage is reached 130 inductance volt.so telephone get humming noise.i put gas dischrge tube individualally still now fault is continued. so i decided to put inductor filter along with line jack unit or rossette box for blocks ac.but i dont know which value select inductor ,resitor .anyone can solve this problem means help me guys. i need blocks the ac inductance voltage...
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