Unless the horns and ceiling speakers are different audio feeds the problem has to be in the power. Try plugging the power into a different AC circuit. A good way to test if noise is being picked up by audio pair is when the noise is happening short the audio pair together and see if it stops.


Merritt

Business Telephones & Equipment + Commercial Audio/Video Products
Commercial Communications . . . Turner, Maine
If it was built after 1980 don't expect it to work right.