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 175 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 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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As Dave said, this should be carried out by someone in the field with working experience with your system and by someone who can held responsible for any faults that may arise.hi selvam
welcome
This is really a problem for your more senior engineers to work out
not people on a forum with no firsthand access to the situation
discuss it with those senior to you
cheers
Dave
The unfortunate part of your problem here is that telecom lines work with a combination of DC and AC... so depending on how you filter the AC noise out, you could very well create problems with DSL, fax, and voice. Additionally, you can't just clamp the voltage to the desired working voltage because the noise would still be present and would most likely be heard as a square wave which is NOT very pleasing to the ear.
It's very unfortunate... but it would seem the line was installed incorrectly. Running signal wires in parallel with noise generating lines is asking for trouble... This is why telecom and power lines are run independently through a home. In cases where this can't be avoided, there are various techniques to prevent noise such as shielding and twisted pair that can be used to help mitigate this.
Once run... it can be very difficult to eliminate noise at either end of the line. I wish for you the best of luck in getting your problem resolved.
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