Thanks for the input. The intercom is built in, and in fact will only work with the radio turned on, though the volume is independent. I usually switch it off when flying solo, and I do have emergency sockets that go straight to the radio. The two headsets are identical, DC 10-30. I will certainly try a sock over the microphone. I too am leaning towards an intercom problem but I would still like an anr headset (well, two of course, one for the other seat as well) if I can make everything work.