Don't assume that you will not receive assistance from Onkyo just because this is not a new purchase...

This isn't a PC manufacturer :), audio companies genuinely TRY to help... (even if they do not help, they at least take your calls)

I have not worked with Onkyo on a regular basis since the mid-90s, but the original idea was to allow cassette decks and CD players from the same mfg/series (with or w/out remotes) to at least be operated in a basic manner from the receiver's remote.

Other items have an "IR In" port on the rear, which is more universal.

what EXACT items are you trying to connect, what EXACTLY are the ports called (if they are not all Onkyo/Integra RI ports), and what EXACTLY are you trying to do with them??

Are you looking to insert a repeating system (Xantech, Niles, etc) so you can place the components inside a cabinet and still operate them via remote??

Are you looking to consolidate remotes to one advanced programmable remote??

If so (on either/both of the examples above), some of these rear ports are compatible, and some are not....
Which is where the "which exact components" question becomes important.

Sometimes the solution is simple... sometimes it involves more advanced steps such as stripping the carrier freq. off the signal in an advanced programmable remote's programming software...