I have a Blackmagic ATEM 4 M/E and one of their studio cameras. I have a headphone on the camera and an active speaker on the ATEM so I can hear talkback.
There is a super loud whine/tone/whistle/noise. It is similar to a 1kHz square tone. Even if I set volume to minimum it is hearable.
What I tried
I tried to disconnect the cable going into "SDI in" from the camera. The tone is still there but only in the ATEM so the source has to be the mixer. I added a mic to the talkback XLR input but it can't be heard. I also tried to add a sound mixer to this same XLR input and even if I set volume to the max it can be barely heard but the tone is still super loud compared to it. What is the problem?