Ever since I installed a 7-station intercom system (hard-wired), 20 years
ago, I had an annoying buzz when I used the system in the evening, i.e. when
three kitchen fluorescent lights were on. The intercom does not buzz when
the lights are off. I am not referring the slight buzzing noise that comes
from the T-12 ballasts, I am referring to the induced buzzing in my
intercom.

How can I eliminate this type of 50-cycle interference? Can I put filter
capacitors in line with the ballasts? How about replacing the old T-12
ballasts with new electronic ballasts and T-8 fixtures? Would that help? I
believe modern ballast operate at a very high frequency. Maybe I should
connect the intercom master unit (also in the kitchen) to a different
electric circuit?

After 20 years, I am getting mighty tired of all this buzzing in the
evening. Of course, it only buzzes when I actually use the intercom to
answer the door or to suggest to my wife to fix dinner.

Thanks for any suggestions from those who have been there, done it.

Walter

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