Intercom dry, shaken, not stirred

Always connecting CCUs to intercom systems? Dreading the seemingly chronic problems?
Here’s one tip. Some CCUs are quite happy to take a dry com line. This means you can completely isolate that feed and really cut down on hum and noise problems. We know for sure that Hitachi CCUs do NOT require the com line to have power. We also know for sure that Sony CCUs MUST have power.