For our new Sony HDC-1400R cameras we are having problems with some of our new intercom headsets.
Some headsets “squeal” when the listen level is turned up to about a 70% level.
Answer: Sony Field Service suggested we try changing the intercom setting from dynamic to manual.  The setting are on the Camera HEAD and not the CCU
Since these were brand new cameras all of the settings were on factory default.  By going into the manual setting mode that allowed us to adjust the intercom mic sensitivity.  It worked perfectlyIt is a menu selection under the intercom settings menu in the camera.  Also, you can set which “ear” has program or PL or both.  That was another problem we were having with the factory settings.  Single muff headsets had only Program.  We had to “mono-ize” the PL and Program to have both in the single muff.