Question:  We purchased several Sony cameras for our studio, they have CCU-D50 camera control units.  The documentation seems to indicate that the intercom connections from the CCU will support balanced 4-wire connections or 2-wire unbalanced party-line connections.  Can you verify that this CCU supports 2-wire Clear-Com party-line connections?  Can I wire multiple CCUs in parallel in 2-wire party-line mode? 
Answer:  The Sony documentation supports balanced 4-wire connections to Matrix frames and unbalanced 2-wire party-line connections to both RTS and Clear-Com IC systems.  The CCU-D50 has a set of intercom dip switches on the rear panel that can be configured for 4-wire, RTS, Clear-Com or 2-wire operation.  See the diagram below for configuration of the dip switches:


















If the user were connecting a single CCU to the existing party-line then it could be setup for Clear-Com 2-wire mode, but if several CCUs are connected in this manner (in parallel) the intercom line impedance will be loaded down and the audio in the intercom line will be reduced significantly to the point of being unusable.
 In this case the CCUs should be treated as 4-wire connections and the use of a Clear-Com 2 to 4 wire interface (model number IF4W4) is highly recommended.  This interface supports up to 4 separate 2 to 4-wire camera connections.  Another interface alternative would be the EF-701M, this supports a single 2 to 4-wire conversion.
The diagram below shows the CCU db-15 intercom pin outs for both 2-wire and 4-wire intercom connections: