I recently bought a TELEX ANR 850 and used it for the first time yesterday on an Airbus but there was a significant problem.
Whenever the intercom is on there is an unbearable high pitch sound in the background. Therefore I had to keep the intercom off. However even with this off ATC complained of a high pitch background noise and so did the cabin crew when I made a PA to the passengers.
Does anybody have any ideas or suggestions as to what this is and how it can be resolved?
I am yet to hear from TELEX as it's the weekend.