That's why I don't have either my 990 or my cable box on an interface module - both require the same one (as best as I can tell, details on the cable box are hard to come by) and I have no interest in buying two of them. If the 990's IR output jack (or the cable box's IR output jack) simply passed the incoming "interfaced" signal back out, though, you could potentially use one interface module for two devices. Just random scheming, though - probably won't ever do it.