Matrix: Interfacing JVC CCU RM-HP790DE to Eclipse matrix

Question: I've finally startedrigging the JVC CCU's with the IF4W4 and PS704 interface modules, so that I can connect them to the Eclipse Pico matrix. I have wiredit according to the document on the Clearcom support page which you linked meto previously (Interfacing JVC's CCU (RM-HP250AU) with common Intercom system)
I'm just having a little problem. It seems that any audio entering the IF4W4(i.e. talkback from a comms panel) is also sent out of the unit back into thematrix, so when a comms panel talks to the camera (with a talk/listen latchopen) they can hear themselves back again. Alternatively, if program soundbeing fed into the PS704 is active, this feed is also on the output of theIF4W4.
I have a document from JVC which is the manual for their CCU unit (which I haveattached to this e-mail, if you could please see page 14) - the model that wehave (RM-HP790DE) says to use the (H) and (C) terminals for comms input,however the Clearcom/JVC document says to just use the (H) and (G) terminals,which is how I have them currently wired.
Answer: a) 2-wire nulling -
when talking from a 4-wire circuit (matrix panels) to a 2-wire circuit (Camera)there is a certain amount of return due to losses in the 2-wire hybrid, thesecan be minimized by nulling the 2/4 wire hybrid. Please make sure you havenulled the IF4W4 using the RLC controls on the IF4W4 unit - see the IF4W4 manualfor details on how this should be done.
This should take-away the problem of the panels hearing themselves
b) looking at the JVC manual you state you have the xxDE version
however we need to use the xxDU version. which uses the H & G connections.
There is a note in the JVC manual see the "*1 " note at the bottom ofpage 14 that talks about the ability to switch the CCU from DE to DU mode.
When you talk to the JVC engineer - please make sure he gives details on how toset the unit into xxDU mode
Reply from customer: I swapped all the CCU's to be the DU mode and nulled theIF4W4 again and it seems to be working very well now. I would estimate a dropof about -30dB from what I had before, which is great. When I latch thetalk/listen on the panel I can barely hear myself back.