walter wrote:
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

Hi,
First thing to do is to find out how the noise is coming into the
intercom system, Through the air or AC wiring. All kinds of things we
can try uing caps. inductors, chokes, etc. Try battery operated AM radio
in the kitchen, do you here buzz?