I had the same problem of noise.
Removal of the music input wires from the intercom input did the trick. Totally quiet now.
A long unterminated cable running parallel to a lot of other cabling picks up the noise.
Shorting the wiring at the jack with a dummy plug has the same effect.
Removal of the music input wires from the intercom input did the trick. Totally quiet now.
A long unterminated cable running parallel to a lot of other cabling picks up the noise.
Shorting the wiring at the jack with a dummy plug has the same effect.