I am just a little curious. Does any one know what the output voltages are from an RFX9x00? Is it 12 volts 5 volts or 3.3. If someone has an oscilliscope they could mesure the envelope swing. A voltmeter will read average or rms voltage since the voltage is actually varying unless you have a peak reading voltmeter that holds the peak value.

I did run across a little circuit that essentially is a level converter using two transistors. Several I know used it to run IR from a slimserver squeezebox output (3.3 volt swing) to a Xantach network (12 volt swing). I used the "optical coupler) as I had the parts laying around. If the output of the RFX9600 is 3.3V then I would expect some trouble with it in a Xantech network. Also the output of the Xantech receivers (I am pretty sure) are either diode Isolated or tristate so as not to load the buss.